The warnings were latest in a flurry of security advisories underlining the continuing threat of terrorism in the world's most populous Muslim country, which has suffered three major attacks by al-Qaeda linked militants since 2002.
"The embassy has learned that as of June 1, 2005, there were plans by extremists to conduct bomb attacks targeting the lobbies of hotels frequented by Westerners in Jakarta. The attacks were to occur circa noon on an unspecified date," the embassy said in a message to US citizens in Indonesia.
It contained no more details, but it follows an unspecified security threat that forced Washington to close its diplomatic facilities in Indonesia last week for four days.
Separately,
"According to our observations, their communications show they are intensively planning to launch more attacks," he told reporters without elaborating .
Militants belonging to the Jemaah Islamiyah terror group have been blamed for three attacks on Western targets in Indonesia in the last three years: the 2002 Bali nightclub bombings; the 2003 bombing of the J.W. Marriott hotel in Jakarta; and last year's attack at the Australian Embassy.
The United States and Australia have warned their citizens to avoid traveling to Indonesia.
After the Bali bombings, some foreign governments faced domestic criticism for not sharing information that militants may have been planning attacks.
