KYIV: Russia and Ukraine met Monday for their first talks since the outbreak of war last week, with Kyiv demanding an "immediate ceasefire" as the number of refugees fleeing the country hit more than 500,000.

As the delegations arrived for talks on the border between Belarus and Ukraine on day five of Moscow's invasion, the Ukrainian presidency demanded the ceasefire "and the withdrawal of troops" -- which Moscow is almost certain to reject.

"I do not really believe in the outcome of this meeting, but let them try," Ukrainian President Volodymyr Zelensky has said.

Severe financial sanctions imposed by the West on Moscow showed their impact on financial markets on Monday morning, with the Russian ruble collapsing to a record low and the Russian central bank more than doubling interest rates to 20 percent.

The sanctions targeting the Russian financial sector are intended to change the calculus of Kremlin leader Vladimir Putin, but on the ground the roughly 100,000 Russian troops thought to be inside Ukraine continued an invasion from the north, east and south.

Western defence officials and the Kyiv government say battling Ukrainian troops have kept the country's major cities out of Russian hands despite incursions in the capital Kyiv and the second largest city, Kharkiv, over the weekend.

"The Russian occupiers have reduced the pace of the offensive," the general staff of the Ukrainian armed forces said Monday, again claiming that Moscow had suffered "heavy losses".

Russian forces seize two small cities in Ukraine

The small southern city of Berdyansk has been occupied by Russian soldiers, however, Ukrainian officials said.

In the capital Monday, after a relatively calm evening, people rushed out to buy food after the lifting of a strict blanket curfew imposed Saturday, with local forces given shoot-on-sight orders over the weekend.

Amid reports of further Russian troop movements towards Kyiv, Moscow said it had now "gained air superiority over the entire territory of Ukraine", while accusing Ukrainian troops of using civilians as human shields.

Putin on Sunday ordered Russia's nuclear forces onto high alert in response to what he called "unfriendly" steps by the West, whose unity and speed in imposing sanctions on the Russian economy has surprised observers.

Putin orders nuclear alert as Ukraine fiercely resists Russian invasion

"The Western sanctions on Russia are hard, but our country has the necessary potential to compensate the damage," Kremlin spokesman Dmitry Peskov told journalists Monday.

Economic pressure

The UN's refugee agency UNHCR said over half a million people have fled Ukraine since the invasion Thursday.

"More than 500,000 refugees have now fled from Ukraine into neighbouring countries," UN refugee chief Filippo Grandi said in a tweet.

The grim figure came as talks got underway at the Belarus-Ukraine border on Monday included Ukraine's defence minister and other officials from Ukraine and Russia.

Kyiv had been initially reluctant to send a delegation to Belarus, given the country's role in facilitating Russia's attack on Ukraine by hosting troops and weaponry used in the invasion.

Putin orders nuclear alert as Ukraine fiercely resists Russian invasion

"We definitely have an interest in reaching some agreements as soon as possible," Vladimir Medinsky, an aide to Putin who has travelled to Belarus for the talks, said in televised remarks.

Zelensky meanwhile issued another video address, wearing his now trademark green khaki sweatshirt, calling on the European Union to agree to "the immediate accession of Ukraine via a new special procedure".

The head of the European Commission, Ursula von der Leyen, gave her personal support on Sunday in an interview with the Euronews channel, but without specifying a timeframe.

"They are one of us and we want them in," she said.

The weekend featured a momentous series of announcements from Europe, with Germany unveiling a historic change in its security and defence policies and the EU saying it would buy and supply arms for the first time.

"With the invasion of Ukraine, we are now in a new era," German Chancellor Olaf Scholz told parliament while announcing a huge hike in military spending that reverses decades of reluctance to invest in defence.

Scholz says Russia will pay bitter price for ‘Putin's war’

The EU announced it would provide 450 million euros ($500 million) for Ukraine to buy weapons, including Russian-made fighter jets that Ukrainian pilots could operate.

It also announced restrictions on Kremlin-run media outlets RT and Sputnik.

Financial hit

Fresh sanctions announced over the weekend on Russia's economy are intended to cut it off from the global financial system, impeding trade with Russian companies and inflicting deep economic pain on the country.

Russia's central bank announced Monday it was more than doubling its key interest rate to 20 percent, dramatically raising the cost of borrowing, because the economy's situation had "drastically changed".

Germany to step up plans to cut dependence on Russia gas

The value of the ruble collapsed against the dollar on Monday, down 20 percent in midday trading, while the Moscow Stock Market was closed for the day.

The ruble was trading at around 100 to the dollar, worth around a third of its value compared with 2014 when Putin annexed the Ukrainian province of Crimea.

Rouble tumbles to record low as West steps up Russian sanctions

The West has prevented some Russian banks from accessing the SWIFT bank system, which is used to settle international trade, and has frozen Russian central bank assets held overseas, depriving Moscow of access to these emergency funds.

The European Central Bank warned Monday that the European subsidiary of the Russian state-owned Sberbank was facing bankruptcy.

EU member states have also closed their airspace to Russian planes.

500,000 fled

International diplomacy is set to continue Monday with the UN General Assembly set to hold a rare emergency session Monday to discuss the conflict.

Elsewhere, efforts to isolate Moscow internationally saw global football body FIFA order Russia to play its home international fixtures in neutral venues and warned it was considering banning it from the 2022 World Cup.

Ukraine has reported 352 civilian deaths, including 14 children, while its army claims that it has killed 4,300 Russian troops.

Russia has acknowledged that a number of its forces had been killed or injured, without giving figures.

Long queues form at central Europe border crossings as people flee Ukraine

The UN human rights chief Michelle Bachelet said Monday at least 102 civilians, including seven children, had been killed in Ukraine.

Putin has said Russia's actions are justified because it is defending Moscow-backed separatists in eastern Ukraine.

The rebels have been fighting Ukrainian government forces for eight years in a conflict that has killed more than 14,000 people.