The UK will send anti-aircraft rockets to Ukraine, capable of shooting down cruise missiles, to help defend its skies against Russian attacks, said Defence Secretary Ben Wallace.
It follows a new wave of deadly missile and drone attacks on Kyiv and other cities this week, with the aim that it will help protect people and infrastructure.
The 'Amraam' rockets are the first donated by Britain that are capable of shooting down cruise missiles.
Vladimir Putin and his forces have been subsequently accused of war crimes by the UK and G7 allies following the latest attacks.
They have vowed to "continue to provide financial, humanitarian, military, diplomatic and legal support and... stand firmly with Ukraine for as long as it takes".
The shift in the Kremlin's strategy to attacks on civilian areas and infrastructure came in retaliation for an explosion that damaged the strategically and symbolically important Kerch Bridge, linking Russia to the annexed Crimean peninsula.
The UK and other western governments are shipping new weapons systems to Ukraine or gearing up to provide more help.
The Amraam rockets will be delivered in the coming weeks to be used with the Nasams air-defence systems pledged by the United States, the Ministry of Defence said.
The latest package of UK equipment also includes hundreds of other air defence missiles and aerial drones, as well as a further 18 howitzer artillery guns.
Defence Secretary Mr Wallace said: "Russia's latest indiscriminate strikes on civilian areas in Ukraine warrant further support to those seeking to defend their nation. So today I have authorised the supply of Amraam anti-aircraft missiles to Ukraine.
"These weapons will help Ukraine defend its skies from attacks and strengthen their overall missile defence alongside the US Nasams."
NATO defence ministers discussed additional support for Ukraine in Brussels on Wednesday, with further talks due on Thursday.
Britain will also give £10 million to the military alliance's funding package to help provide humanitarian assistance to Ukraine including winter clothes, shelters, generators, fuel trucks and ambulances.
The UK has previously supplied Kyiv with various weapons, including the NLAW anti-tank missile launcher, which was considered instrumental in the initial defence against Moscow's invasion.
US Defence Secretary Lloyd Austin said he expected that Ukraine would do everything it could throughout the winter to regain its territory.
"And we're going to do everything we can to make sure that they have what's required to be effective," he told a news conference in Brussels.
Germany said on Wednesday the first of four IRIS-T air defence systems had reached Ukraine.
