Ukraine's ability to move exports by sea has been severely impacted since Russian President Vladimir Putin's invasion of Ukraine in February 2022 and his blockade in the Black Sea.

"These minehunters will deliver vital capability to Ukraine which will help save lives at sea and open up vital export routes," Defence Secretary Grant Shapps said.

The transfer of the vessels to Ukraine's armed forces comes with Shapps and his Norwegian counterpart due to launch a new defence initiative later Monday, the Maritime Capability Coalition.

"This capability boost marks the beginning of a new dedicated effort by the UK, Norway and our allies to strengthen Ukraine's maritime capabilities," Shapps said.

The initiative will enhance Ukraine's ability to defend its sovereign waters and bolster security in the Black Sea, he said.

The transfer was agreed through meetings of the 50-nation strong Ukraine Defence Contact Group.

British Prime Minister Rishi Sunak has repeatedly stressed "unwavering" support for Ukraine with pound4.6 billion ($4.9 billion) in military backing allocated since the invasion, the government said.

Shapps was also expected to announce further details of UK military support to Ukraine at the launch.