Negotiators from Ukraine and Russia scheduled an initial round of talks after four days of a Russian military onslaught on its southern neighbour with no decisive breakthrough, while new explosions were heard in Kyiv and other cities.

Russia’s financial markets were gripped by turmoil as they reopened after the weekend, with the rouble plunging nearly 30 percent against the dollar – after the European Union announced tough new punitive measures against Moscow, including funding for new weaponry for Kyiv, the removal of Russian banks from the Swift payment system and a Europe-wide bar on Russian aircraft.

Putin cited the new sanctions as one of the reasons for placing Russia’s deterrence forces, including nuclear weapons, on high alert. Western countries roundly condemned the move, though it does not mean Russia will resort to using them.

The United Nations Security Council was due to hold another sitting on the crisis after a resolution submitted to the body last week was derailed by a veto imposed by permanent member Russia.

Air raid sirens wailed across Kyiv and other cities from dawn as Russian attacks resumed. Shelling was reported in the city of Chernihiv north of the capital, but in Kharkiv, Ukraine’s second city, authorities said they were in full control after street battles on Sunday.

Kyiv remained under a round-the-clock curfew, due in theory to be lifted later in the day. Residents remained holed up in shelters or in the city’s deep metro system. European officials said some 300,000 people had already fled the country – many of them going to Poland and Moldova. Vast numbers of other Ukrainians headed towards western regions of the country deemed to be safer.

Defence minister vows to defend the capital

“We will not give up the capital, Ukraine is already winning,” Defence Minister Oleksiy Reznikov said on Monday morning, remarking on “96 hours of resistance” and “4 days of dedication, courage and faith” for the Ukrainian people.

“The enemy who came to our land will go in a known direction. Therefore, we advise the occupiers to go home. It’s not too late. It is useless to intimidate Ukrainians. It will not be possible to break our defenders.”

British officials said Ukrainian President Volodymyr Zelensky, in a call with Prime Minister Boris Johnson,  had described the coming 24 hours as “decisive” in efforts to defend the country against the overwhelming force of Russia’s army.

Zelensky negotiated the terms of the talks – scheduled for an area of Ukraine’s border with longstanding Russian ally Belarus near the Pripyat River. He had earlier refused a Russian proposal to hold the meeting in the Belarusian capital Minsk, site of earlier discussions to end eight years of conflict pitting Ukraine’s army against Russian proxies in the country’s eastern Donbas region.

The Ukrainian president said the talks were taking place without preconditions with the hope of limiting casualties and there were no plans to submit to any Russian demands. But he had little hope they would produce results.

“Of course, we want peace, we want to meet, we want for the war to end,” Zelensky said earlier as the terms of the meeting were under discussion. “Warsaw, Bratislava, Budapest, Istanbul, Baku — we have suggested all that to Russia.”

The talks were to go ahead after officials in Kyiv noted that rockets aimed at Ukrainian targets had for the first time been fired from Belarus – where large numbers of Russian troops were deployed for exercises as part of the months-long buildup of troops along Ukraine’s border. Some military sources said Belarusian troops would soon join Russian forces in the mass incursion into Ukraine.

And on Sunday, Belarusian voters in a referendum backed amendments to the constitution strengthening the powers of authoritarian ruler Alexander Lukashenko and rescinding the country’s post-Soviet neutral status. Analysts said that could pave the way for deployment of Russian nuclear weapons surrendered to Moscow by both Belarus and Ukraine in the aftermath of the Soviet collapse.

Putin referred to “aggressive statements” by NATO and tough financial sanctions in issuing a directive to increase the readiness of Russia’s nuclear weapons, raising fears that the invasion of Ukraine could lead to nuclear war, whether by design or mistake.

“This is dangerous rhetoric. This is behaviour which is irresponsible,” NATO Secretary General Jens Stoltenberg told CNN.

“If you combine this rhetoric with what they’re doing on the ground in Ukraine- waging war against the independent sovereign nation, conducting full fledge invasion of Ukraine- this adds to the seriousness of the situation.”

Ukraine’s intention to secure NATO membership—and the presence of NATO weaponry in other east European states – are at the heart of the Russian decision to move into Ukraine despite weeks of denying it had any intention of doing so.

Eight years after annexing the Crimean peninsula and fomenting a separatist rebellion in eastern Ukraine, Putin accused the West of failing to respond to his calls for “security guarantees” that the Alliance would undergo no further expansion and Ukraine would never be allowed to join.

He also accused Ukraine of committing “genocide” against Russian-speakers in Donbas and urged Ukrainian servicemen to stage a coup against the country’s leaders, made up of “a gang of drug addicts and neo-Nazis”.

But Russia’s advance on Kyiv and other cities has clearly encountered problems in running up against determined Ukrainian defenders and large numbers of volunteers taking on guns and manufacturing petrol bombs en masse.

Russian casualties

Deputy Ukrainian Defence Minister Hanna Malyar put the number of dead Russian servicemen at 4,300 after four days of fighting as well major equipment losses — 146 tanks, 27 aircraft and 26 helicopters. Russia’s Defence Ministry acknowledged for the first time it had suffered casualties, but gave no figures.

Video posted on social media showed Russian armoured vehicles bogged down some distance from city centres and smoke pouring from them in some cases.

Fresh protests against the invasion were staged world-wide, with a march in Berlin attracting 100,000. Protests were also staged in Russia, with rights monitors saying than 2,000 people were detained in the latest demonstrations, bringing the total number of arrests to more than 5,000.

In Brussels, the European Union approved funds for the purchase of 500 million euros in weaponry to be provided for Ukraine. The EU also spearheaded a drive to bar all Russian aircraft, both commercial and private, from the 27-member bloc. Several Russian aircraft were forced to alter course or turn around in mid-flight. Other airlines ordered long-term cancellation of flights in anticipation of the move.

European Commission President Ursula von der Leyen said Ukraine belonged in the EU and she would work towards advancing the process of admitting the country.

“We have a process with Ukraine that is, for example, integrating the Ukrainian market into the single market,” von der Leyen told Euronews in an interview.

“We have very close cooperation on the energy grid, for example. So many topics where we work very closely together and indeed over time, they belong to us. They are one of us and we want them in.”

In Moscow, the rouble dropped some 28 percent to almost 118 against the dollar after the weekend imposition of increasingly stringent punitive measures against Russia. In response, Russia’s central bank banned foreign selling of Russian securities and gave no details on when the ban would be lifted. The central bank also said trading on Russia’s stock markets would not open for the morning session. The benchmark Moex index has fallen by more than a quarter over the past week.

Over the weekend, British petroleum major BP announced it was abandoning its stake in Russian oil giant Rosneft in a costly end to three decades of operating in the country. It was the most significant move yet by a Western company in response to Moscow’s invasion of Ukraine – BP was the biggest foreign investor in Russia.

In Berlin, German Chancellor Olaf Scholz told a special Sunday session of Parliament that Germany would increase its military spending to more than 2 percent of the country’s economic output, beginning immediately with a one-off 100 billion euros, or $113 billion, to invest in the country’s armed forces.

He added that Germany would speed up construction of two terminals for receiving liquefied natural gas, or LNG, part of efforts to ease the country’s reliance on Russian energy.

On Saturday, Germany Germany abandoned its frequently criticised reluctance to provide military hardware, saying it would supply Ukraine with 1,000 anti-tank grenade launchers and 500 stinger surface-to-surface missiles.

The U.S. State Department said it would send $350 million in weapons to Ukraine, including Javelin anti-tank missiles, anti-aircraft systems and body armour. The Netherlands announced the deployment of 50 Panzerfaust-3 anti-tank weapons and 400 rockets.