Japan lodged a protest last month over Medvedev's visit to Iturup, one of the islands known in Russia as the Southern Kuriles.

Thousands entered Croatia from Serbia earlier this week after Hungary fenced off its Serbian border and sealed shut the previous route north.

The overnight air strikes targeted two training camps belonging to the Islamist group Hamas, causing no injuries, officials and witnesses said.

In London, U.S. Secretary of State John Kerry said the United States was looking to find "common ground" with Russia.