Indonesian police on Saturday arrested 11 members of an Islamic group allegedly planning attacks on American diplomatic missions, a spokesman said, in the latest terror alert to hit the country.
The group had planned to hit the US embassy and a US consulate, as well as a building near the Australian embassy in the capital Jakarta that houses the office of American mining giant Freeport-McMoran, police said.
Police said they were from a new outfit called HASMI, the Sunni Movement for Indonesian Society, and explosives and a bomb-making manual were found when members were arrested in locations across the main island of Java.
"The group's objectives were to attack the US embassy in Jakarta and consulate-general in the eastern Javanese city of Surabaya," national police spokesman Suhardi Alius told reporters.
Indonesia has waged a long battle against terrorism since the 2002 Bali bombings that killed 202 people, mostly foreign tourists. The resort island held commemorations this month to mark 10 years since the attack.
Indonesia has not seen a major attack since 2009, when suicide bombers killed nine people in attacks on two five-star hotels in the capital.
Alius said that those arrested Saturday were "suspected terrorists" who were "part of a new network known as HASMI". They are from the Sunni branch of Islam, which is the predominant one in Indonesia.
Previous deadly attacks, including the Bali bombings, have been blamed on the Al-Qaeda-linked Jemaah Islamiyah (JI), but authorities say the group has been severely weakened by the crackdown on terrorism.
However, smaller Islamist groups seeking to create an Islamist caliphate through violent means have emerged.
Anti-terror police made Saturday's arrests in four cities across Java: four in Jakarta, two in Madiun, three in Solo and two in Bogor.
Explosive materials were found in Solo and in Bogor, which is on the outskirts of the capital.
"We also confiscated an explosive device from a home in the town of Madiun in eastern Java, as well as explosive materials and a bomb-making manual," Alius said.
He said one device consisted of a cylinder packed with explosives. The bomb-making manual was in English and the Indonesian language and was likely downloaded from the Internet, he added.
Alius added that police were looking into the group but added that "if they can already build bombs, we can assume they've been around for some time".
Saturday's arrests came after two policemen were found murdered this month while investigating an alleged terrorist training camp in central Sulawesi's Poso district.
Police said they had been investigating an alleged camp linked to Jemaah Anshorut Tauhid (JAT), declared a terrorist organisation by the United States in February.
And before this month's ceremony to commemorate the Bali bombings, Indonesia declared its top security alert citing "credible information" of a threat to the event, which was attended by Australian Prime Minister Julia Gillard.
Freeport-McMoran's Indonesian subsidiary runs the world's biggest gold and second-biggest copper mine in the restive Papua region, employing more than 20,000 people.