American and Serbian paratroopers have held joint exercises in Serbia, watched with unease by Russia which is trying to increase its influence in the Balkans.

Serbian President Aleksandar Vucic attended the last day of the four-day drills that included joint jumps by Serbian and US troops from two US Air Force C-130J Hercules transport planes close to the Serbian capital, Belgrade.

Mr Vucic said: "The joint exercise contributes to the (military) skills, but also enhances partnership and friendship that was not always seen in the past."

American and Nato-related military activities in the Balkans regularly trigger anger from the Kremlin, which opposes the Western military alliance's expansion in the former communist eastern Europe.

Serbia, which tries to balance politically between Russia and the West, claims military neutrality.