This year's Eurovision Song Contest host Ukraine may ban Russia's competitor from entering the country following reports the singer has visited Crimea since the peninsula was seized by Russia, Ukraine's state security service (SBU) says.

Russia's annexation of Crimea in 2014 sent relations with Ukraine to an all-time low and now even sporting or cultural events are potential sources of tension between the two.

Ukraine, which won the right to stage the 62nd Eurovision event after its contender won the 2016 competition, has previously said it would deny entry to certain Russian singers it deemed anti-Ukrainian.

On Sunday, Russia announced singer Yulia Samoylova, 27, as its entrant for this year's contest.

The Kremlin denied she had been picked out of a desire to provoke Ukraine politically and said the choice was made independently by state-run broadcaster Channel One.

"It's clear that one should wish to avoid any politicisation of Eurovision and we believe it is absolutely unacceptable," Kremlin spokesman Dmitry Peskov told journalists on a daily conference call.

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It is uncertain whether a ban from entering Ukraine would eliminate Samoylova from the competition or if she could compete remotely. Requests for clarification sent to Eurovision organisers did not receive an immediate response.

"The SBU is looking into the issue and will take a considered decision on her entry into Ukrainian territory," SBU spokeswoman Olena Gitlianska said in a post on Facebook.

She said the decision would be based on Ukrainian law, according to which Ukraine reserves the right to ban citizens who have visited Russia-controlled Crimea without obtaining prior permission from Kiev.

Last year Russia accused Ukraine of politicising the competition by choosing as its entrant a Crimean Tatar named Jamala whose song decried war-time deportations of Tatars under Soviet leader Joseph Stalin in the 1940s.

Ukraine expects about 12,000-14,000 spectators to attend the competition in May with millions more watching on television.