MOGADISHU (Reuters) - Somalia's Islamist movement denied on Monday that dozens of its fighters had surrendered to the interim government, and vowed to continue fighting government troops and their Ethiopian military allies.

"No Islamist fighter has united with the government," said Sheikh Mohamud Ibrahim, a spokesman for the sharia courts group.

"Our fight against the Ethiopians and their puppet government is based on an Islamic ideology and it will continue until the Islamic law, which was deprived from the Somali people is restored," he added.

Ibrahim was responding to a police report that 49 Islamist gunmen handed themselves over to the government at the weekend.

Local human rights activists say 6,500 people were killed last year in fighting between allied Somali-Ethiopian forces and Islamist insurgents in the capital Mogadishu.

The government, supported by Ethiopian soldiers, is struggling to put down an insurgency in Mogadishu by remnants of the Islamist movement they routed just over a year ago.

In a separate development, a Somali journalist was freed on Monday after spending nearly a month in jail, accused of collaborating with the Islamists.

Bashir Mohamed Abdulqadir, a reporter for Somaliweyn Radio in Mogadishu, was arrested by government intelligence agents on January 13.

"I was released today," he told Reuters by phone. "They ... accused me of working with the Islamic Courts, but I have been found innocent."