BANDA ACEH - Eleven people were injured when a hand grenade was thrown into a crowd gathering to celebrate Indonesia's Independence Day, in the troubled province of Aceh, police said. Police said none of the injuries was serious. The blast occurred on a soccer field about an hour before the morning ceremony was due to begin, police said. Rebels in Aceh - on the northern tip of Sumatra - have been fighting for independence since 1976. The violence has claimed thousands of lives and rights activists accuse the military of abuses including torture, kidnappings and assassinations. The separatists often launch attacks on and around August 17, the day marking Indonesia's declaration of independence from Dutch colonial rule in 1945.