Blast injures 2 Russians after Putin-Bush summit

(Changes source, adds details)

MOSCOW, April 7 (Reuters) - An explosion injured two people in the Russian Black Sea resort of Sochi hours after Russia's President Vladimir Putin met U.S. leader George W. Bush at his villa on the outskirts of the city.

Russian news agencies on Monday initially quoted a security source as saying a bag left outside a cinema had exploded on Sunday, severely injuring a policeman.

Police later said in a statement the policeman, who was off-duty, and a friend had set off the blast themselves by playing with a grenade.

"The policeman and his acquaintance decided to experiment with concussion grenades," the statement said. "The result was that two people were injured including, the policeman."

Concussion grenades fragment less than a normal hand grenade and are designed for use in enclosed areas.

Bush was in Sochi for a two-day summit with Putin, their last meeting before the Russian leader's term ends next month. Bush's aircraft took off from Sochi soon after midday (0900 GMT). The blast was at 10:00 p.m., the police statement said.

Sochi is due to host the 2014 winter Olympics. It lies on the edge of the volatile Caucasus region and is only a few hours drive from Chechnya where rebel bombs occasionally kill Russian security forces. (Writing by James Kilner; Editing by Dominic Evans)