Authorities released from jail six Americans and four other foreigners charged with violating the country's territorial waters but kept them under city arrest until a court decides their case.

The group includes three Australians and a Briton and some members threatened Monday to launch a hunger strike to try to expedite the proceedings. The 10 were arrested March 22 for allegedly entering Indonesian waters without a proper permit in the eastern Sumatra province of Riau, a few miles south of Singapore.

A local news report quoted one of the Americans as saying the group was on a scuba diving holiday looking for a sunken wreck when they were arrested.