Russia's prime minister Dmitry Medvedev has arrived in Crimeaas the most senior Russian government official to visit the region since it was annexed.

Medvedev flew in to Crimea's main city of Simferopol with a delegation of Russian ministers as Moscow sought to solidify its claim over the region.

He tweeted on his official Twitter account:

His visit came after US secretary of state John Kerry and Russian foreign minister Sergei Lavrov held talks in Paris, without a breakthrough.

Lavrov demanded that Ukraine become a neutral state, without moving closer to the European Union or Russia. Kiev rejected his proposal as an attempt to prevent Ukraine from joining the EU.

Russian troops have seized three military bases in Crimea following President Vladimir Putin's annexation of the Russian-dominated region after a local referendum in the peninsula found in favour of closer ties to Moscow.

Fears were growing that Putin has set his sights on other areas with prominent Russian-speaking populations or a place in Russia's Tsarist and Soviet history, including Transnistria, Finland and Belarus.

Latvian foreign minister Edgars Rinkevics said that Latvia was "concerned" by Russia's recent actions.

"We are very much concerned about what is happening in Ukraine but we are not hysterical," Rinkevics said.