LONDON (AFP) - British Foreign Secretary William Hague will visit Kiev on Sunday for talks with the interim Ukrainian government as tensions rise with Russia over Crimea, a Foreign Office spokesman said.

The spokesman had no further details about the trip, but Mr Hague tweeted overnight: "Have just spoken to Acting President (Oleksandr) Turchynov.

"I will travel to Kiev on Sunday for talks with the new government."

Mr Turchynov had appealed to Russian President Vladimir Putin on Friday to "stop military provocation" and withdraw from Crimea, after pro-Russian gunmen seized the government and parliament buildings in the capital Simferopol.

British Prime Minister David Cameron had earlier called Mr Putin to stress the importance of respecting Ukraine's territorial integrity.

US President Barack Obama has also said he is "deeply concerned" by reports of Russian military movements in Ukraine, and warned there would be "costs".