(Reuters) - Ukraine retains control over the majority of its airspace, Britain's defence ministry said on Wednesday, adding that Russia has failed to effectively destroy the country's air force or suppress its air defences.

"Russia has very limited air access to the north and west of Ukraine, limiting offensive actions to deep strikes with stand-off weapons," it said on Twitter.

"Russian air activity is primarily focused on southern and eastern Ukraine, providing support to Russian ground forces," the ministry added in a regular bulletin.

Russia continues to target Ukrainian military assets and logistics infrastructure nationwide, British military intelligence said in the update.

It flagged a higher risk of civilian casualties, saying most Russian air strikes in the Ukrainian port city of Mariupol were probably using unguided free-falling bombs.

"These weapons reduce Russia’s ability to effectively discriminate when conducting strikes, increasing the risk of civilian casualties."