Boris Johnson is set to announce a new military support package for Ukraine on Thursday as he meets with NATO and G7 leaders and urges them to "step up" in response to Russian aggression.

Calling on the UK's allies to ensure Ukrainian's have the means to continue to protect themselves against Russian President Vladimir Putin's forces, the prime minister will pledge 6,000 new defensive missiles and £25m in financial backing for Ukraine's military personnel.

The measures more than double the defence lethal aid provided to date and comes on top of the £400m the UK has committed in humanitarian and economic aid for the crisis so far, the government said.

Leaders of G7 and NATO member states will convene for talks in Brussels tomorrow to discuss longer-term military, diplomatic and humanitarian support for Ukraine and how they propose to strengthen measures against Russia.

PM to urge world leaders to continue united front

One month into the conflict, Mr Johnson is expected to call on the international community to continue in its unified stance on Ukraine and collective action on economic, military and diplomatic measures.

He is also set to urge the UK's allies to step up a gear in response to Russia's use of increasingly brutal tactics, including by doubling down on economic sanctions against the Kremlin.

"Vladimir Putin is already failing Ukraine," the PM will say.

"The Ukrainian people have shown themselves to be extraordinarily brave and tenacious in defending their homeland, in the face of an unprovoked onslaught.

"But we cannot and will not stand by while Russia grinds Ukraine's towns and cities into dust. The United Kingdom will work with our allies to step up military and economic support to Ukraine, strengthening their defences as they turn the tide in this fight.

"One month into this crisis, the international community faces a choice. We can keep the flame of freedom alive in Ukraine, or risk it being snuffed out across Europe and the world."

The £25m in new funding will help pay the salaries of Ukrainian soldiers, pilots and police and ensure the armed forces are well equipped with high-quality equipment.

Zelenskyy issues warning of fresh attacks

It comes after Ukraine's president warned Russian forces are using the Chernobyl exclusion zone to prepare fresh attacks.

Volodymyr Zelenskyy issued his warning - citing no evidence - during a virtual speech to the Japanese parliament this morning.

The Russian military seized the decommissioned plant at the beginning of the month-long war. The exclusion zone is the contaminated area around it, where the world's worst nuclear meltdown happened in 1986.

President Zelenskyy said on Wednesday afternoon that Boris Johnson had offered "assurances of his support" ahead of an extraordinary NATO summit on Thursday.

The two men discussed the "course of hostilities and defence assistance to Ukraine", Mr Zelenskyy tweeted, adding: "We will win together."

Commenting on the conversation between the PM and Mr Zelenskyy, a Downing Street spokesperson said: "The prime minister set out his intention to use tomorrow's G7 and NATO meetings to increase the pressure on Vladimir Putin's regime and work with partners to substantively increase defensive lethal aid to Ukraine.

"Leaders would look to address Ukraine's requests and ensure President Zelenskyy is in the strongest possible position in ongoing peace talks."

NATO chief issues nuclear war warning to Moscow

On Wednesday, NATO Secretary General Jens Stoltenberg warned against the conflict sliding into a nuclear confrontation between Russia and the West.

He said Moscow "should stop this dangerous, irresponsible nuclear rhetoric" and that it "must understand that it can never win a nuclear war" - in response to a question from Sky News correspondent Mark Stone.

The government will also provide the BBC World Service with an additional £4.1m in emergency funding to support its Ukrainian and Russian language services in the region and help it create content to counter disinformation about the war in Ukraine.

The money will be provided by the Department for Digital, Culture, Media and Sport and the Foreign, Commonwealth and Development Office.

The UK has already provided more than 4,000 anti-tank weapons to Ukraine's armed forces, including Next-Generation Light Anti-Tank Weapons Systems, or NLAWs, and Javelin missiles.

Justice Secretary Dominic Raab will also chair a meeting of justice and foreign ministers in the Hague on Thursday to coordinate support for the International Criminal Court's war crimes investigations.

He is expected to announce an additional £1 million in funding for the court, as well as new support from UK soldiers with expertise in intelligence gathering.