More British weapons will be sent to Ukraine in response to the looming threat of a full-scale invasion by Russia.
British prime minister Boris Johnson said lethal defensive weapons and non-lethal aid would be sent to the country.
The UK has already sent anti-tank weapons to the Ukrainian military to help counter the threat posed by Russian forces ringed around the country’s borders.
The prime minister said: “In light of the increasingly threatening behaviour from Russia, and in line with our previous support, the UK will shortly be providing a further package of military support to Ukraine.
“This will include lethal aid in the form of defensive weapons and non-lethal aid.”
Earlier UK foreign secretary Liz Truss warned Britain will make it “as painful as possible” for Russia if president Vladimir Putin unleashes an all-out attack on Ukraine.
Ms Truss said the Russian leader appears to be “hell-bent” on invading his neighbour, including potentially an assault on the capital Kyiv.
She said the UK government has further measures “in the locker” which it could activate, after an initial tranche of sanctions announced on Tuesday was widely criticised as being too weak.
Mr Johnson told MPs that three oligarchs linked to the Kremlin and five smaller Russian banks were being targeted in the “first barrage”, as the United States and the European Union unveiled similar measures.
It follows Mr Putin’s announcement that Russia would recognise the breakaway “republics” of Donetsk and Luhansk in eastern Ukraine, a move seen by many in the West as a precursor to a full-scale invasion.
Ms Truss has said the UK is also considering sanctions for members of the Russian Duma and Federation Council, and extending Crimea’s territorial sanctions to the separatist-controlled territories in the Donbas.
Shadow foreign secretary David Lammy said on Wednesday morning that the UK government needs to act now.
“I think the mood of the entire House of Commons yesterday was that the Government were not being strong enough,” he told BBC Breakfast.
“The Labour Party, of course, but also other parties and backbenchers in the Conservative Party, (are) hugely concerned that we’ve not been strong or hard enough – sending a message to Vladimir Putin that might, at this 11th hour, make him step back.”
Britain’s sanctions announced on Tuesday targeted three “very high net wealth individuals” – Gennady Timchenko, Boris Rotenberg and Igor Rotenberg – who are described as “cronies” of the Russian president.
Measures, which include UK asset freezes, a travel ban and prohibition on British individuals and businesses dealing with them, were also tabled against Russian banks Rossiya, IS Bank, General Bank, Promsvyazbank and the Black Sea Bank.
Russia is currently estimated to have 150,000 troops massed on the borders around Ukraine, with warplanes and armoured vehicles continuing to deploy in the area.
Mr Putin has said the only way to resolve the crisis is for the government in Kyiv to give up its ambitions to join Nato and to accept the “demilitarisation” of the country.