Prosecutors in Thailand have formally charged five alleged members of the regional terror group Jemaah Islamiyah with plotting attacks on foreign embassies and tourist locations.

The four Thais and one Singaporean escaped being charged under Thailand's new anti-terrorism law, which allows for the death penalty. Because their alleged crimes pre-date the new law, they instead face up to 10 years in jail if convicted.

Three of the Thais, a religious teacher, his son and a doctor, were arrested in June. The fourth Thai surrendered in July. The Singaporean was arrested in May and handed over to his country.

They are charged with conspiring to harm national security. Police say they were working with suspected Jemaah Islamiyah chief Hambali, who was arrested in Thailand last month. He is being interrogated by U.S. authorities at an undisclosed location.

Meanwhile, Singapore authorities have warned local hotels, shopping centers and other commercial buildings to boost their security to guard against terrorism. Home Affairs Minister Wong Kan Seng was one of a number of government officials who voiced the warning Tuesday at a conference of some 300 business people.