‘Hundreds’ died in Mariupol theatre bombing, city council says, as Biden to meet Ukrainian refugees

President Joe Biden visits Poland later today – home to more than two million Ukrainian refugees – after earlier warning that NATO would respond “in kind” if Russia uses chemical weapons.

The refugee crisis will be one of the key issues as he meets Poland’s president, while he will also visit US troops stationed in Rzeszow, near the Ukraine border.

Before that, there will be a meeting with European Commission President Ursula von der Leyen in Brussels, which hosted a summit of NATO and G7 leaders in Brussels on Thursday.

It was there that the US leader called Russian President Vladimir Putin a “brute” and said any chemical attack “would trigger a response in kind” – but that NATO would “make that decision at the time”.

“The nature of the response will depend on the nature of the use,” added Mr Biden.

Ukraine news live: NATO to provide four more battle groups in Eastern Europe

Fears have been growing that Mr Putin could use chemical weapons to try to speed up Russian military gains, which experts say has been far slower than expected.

Prime Minister Boris Johnson was also at the NATO meeting and warned of “very, very severe” consequences if Russia used chemical or biological weapons.

NATO has repeatedly insisted it will not send any of the alliance’s troops into Ukraine.

In other developments:

• Russia’s deputy UN ambassador says it would use nuclear weapons if ‘provoked’
• Chelsea owner Roman Abramovich played early role in peace talks, Kremlin claims
• At least 1,035 Ukrainians have died and 1,650 wounded, says UN; but real number likely much higher
• Unlikely beacon of light for desperate families fleeing the devastated city of Mariupol

PM denies Kremlin claim he’s ‘anti-Russian’

Mr Johnson also hit back at comments that appeared to single him out as Russia’s most-hated leader.

Kremlin spokesman Dmitry Peskov called the prime minister “the most active participant in the race to be anti-Russian”, according to state news-agency RIA.

Mr Johnson told reporters he was “not remotely anti-Russian” and that no one involved in the international talks was against the Russian people.

Another 6,000 missiles will also be sent to Ukraine in addition to the 4,000 already supplied, Mr Johnson revealed on Thursday.

Read more: Unlikely beacon of light as families flee Ukraine’s most devastated city

More sanctions imposed as NATO bolsters defences

NATO, meanwhile, is bolstering defences in Eastern Europe, with four new battle groups in Hungary, Romania, Bulgaria, and Slovakia.

Sanctions are also ramping up, with Britain, the US, Australia, and Japan issuing an expanded list.

Liz Truss, the UK foreign secretary, said the Wagner Group of Russian mercenaries – believed to be tasked with killing Ukraine’s President Volodymyr Zelenskyy – was among its 65 new targets.

US claims high failure rate on Russian missiles

The war – which the Kremlin calls a “special military operation” – has seen brutal shelling of civilians in many cities, such as Mariupol in the south, where thousands hide in basements without power and little food and water.

However, progress around the capital Kyiv appears to have ground to a halt in recent weeks and no major cities have been captured.

Failure rates for some of Russia’s precision-guided missiles are reportedly as high as 60% – and it’s now running out of the weapons, according to US officials, speaking anonymously to the Reuters news agency.

Ukraine’s authorities claim Russia has lost “15,800 personnel”, but NATO estimates it at between 7,000 and 15,000 Russian deaths.

Ukraine mounting successful counterattacks

Buoyed by an influx of weapons from the West, Ukraine also appears to be having some notable success in its counterattacks.

Pictures appear to show a Russian landing ship on fire near Berdyansk, which was seized on 27 February.

Despite the slow progress, Ukraine military officials said on Thursday that Russia was attempting to restart efforts to capture Mariupol, as well as Chernihiv, Sumy, Kharkiv, and Kyiv.

The “first full-fledged” exchange of prisoners of war has also taken place, according to Ukraine’s deputy PM.

Iryna Vereshchuk said 11 Russian civilian sailors had been handed back after being rescued from a sunken ship near port city Odesa.

In return, 19 Ukrainian civilian sailors are said to have returned home after their ship was captured.

Zelenskyy: Western aid came ‘a little late’

President Volodymyr Zelenskyy marked a month of war in his latest video message late last night.

“The 30th day. It’s been a month! If Russia had known it would face that, I’m sure they would have definitely been afraid to come here,” he said.

Despite both sides saying peace talks were progressing, the fighting goes on, and Mr Zelenskyy says a head-to-head with Mr Putin is needed to end the bloodshed.

The president earlier thanked the West for its “strong steps” on sanctions, but told leaders at the Brussels summit “it was a little late”.

“Because if it had been preventive, Russia would not start a war,” he told them via video link.

Mr Zelenskyy did not bring up his demand for a no-fly zone, but instead asked for “1% of all your planes, 1% of all your tanks” – a request Boris Johnson later described as logistically “very difficult”.

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Western nations are, however, said to be weighing up providing anti-ship weapons amid fears Russia will launch amphibious assaults on the country’s Black Sea coast.

The region has seen some of the fiercest attacks, with Russia believed to be trying to establish a land corridor to Crimea and areas under rebel control in the east.