The Ministry of Defence (MOD) has announced it will send helicopters to Ukraine for the first time since the war began.
Defence Secretary Ben Wallace said it will be the first time piloted aircraft are sent to the war-torn nation since Russia's invasion.
The first of the Sea King aircraft has already arrived in the country.
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The Royal Navy has trained 10 crews of the Armed Forces of Ukraine and engineers on the Sea King, the MOD said.
The Sea King gave decades of service to the Royal Navy and Royal Air Force, in many operational roles.
The helicopter was used for anti-submarine warfare, search-and-rescue missions, general duties, carrying Royal Marines commandos into action in the Falklands, Iraq, the Balkans, Sierra Leone and Afghanistan.
Mr Wallace, who made the announcement from Oslo where he is meeting allies to discuss ongoing military support for Kyiv, added that the UK will also send an additional 10,000 artillery rounds.
He said: "Our support for Ukraine is unwavering. These additional artillery rounds will help Ukraine to secure the land it has reclaimed from Russia in recent weeks."
The announcement comes after Prime Minister Rishi Sunak used a visit to the Ukrainian capital Kyiv to set out a new £50m package of defence aid which included 125 anti-aircraft guns and equipment to counter deadly Iranian-supplied drones, including dozens of radars and anti-drone electronic warfare capability.
The package follows more than 1,000 new anti-air missiles announced by Defence Secretary Ben Wallace earlier this month.
The UK is bolstering its training offer to Ukraine's armed forces, sending expert Army medics and engineers to the region to offer specialised support and is also sending tens of thousands of extreme cold winter kits for Ukrainian troops.
The Defence Secretary is hosting a meeting of the Northern Group of defence ministers on board Royal Navy aircraft carrier HMS Queen Elizabeth.
It is expected to address Russia's invasion of Ukraine, northern European security and Sweden and Finland's NATO membership applications.
The group, a British initiative, aims to foster more efficient and effective defence and security cooperation in northern Europe, the MOD added.
Its members are Denmark, Estonia, Finland, Germany, Iceland, Latvia, Lithuania, the Netherlands, Norway, Poland, Sweden and the UK.