Candra Malik & Farouk Arnazp, Solo – Police in Central Java are investigating a worrying surge in attacks or attempted attacks on churches and police stations there over the past week, which a source has linked to an Islamic militant group.

Since Nov. 30, police have found and defused bombs at three churches and three police stations, while one church has been firebombed and another shot at.

The latest attack occurred early on Tuesday, when unknown assailants threw two Molotov cocktails at the Kristus Raja Church in Gawok subdistrict in Sukoharjo. No casualties or significant damage were reported. Police recovered cables, a 9-volt battery, aluminum pipe fragments and nail fragments from the scene.

Later the same day, police found a homemade bomb in the yard of the Pasar Kliwon subprecinct police station in Solo. The bomb was successfully defused.

On Sunday, a janitor at the Muria Indonesia Church in Solo's Serengan subdistrict reported that glass surrounds of the church balcony had been shot, and a high-caliber projectile was found inside the building.

Last Thursday, a low-yield bomb was found at the Bunda Maria Convent in Prambanan subdistrict, Sleman. It had failed to detonate because of a faulty timer.

Two days earlier, police in Klaten district found and defused bombs at two churches and two police stations there.

Central Java Police Chief Insp. Gen. Edward Aritonang said on Wednesday that police were investigating whether the incidents were linked, but said the bombs found in Sleman and Klaten were different from that found at the Pasar Kliwon police station.

"We're still investigating the cases, including the alleged shooting of the Muria Indonesia Church, and hunting down the perpetrators," he said. "Whoever they are, they're terrorists."

A police source told the Jakarta Globe that the National Police's counterterrorism squad was on high alert following the incidents in Central Java. "We've dispatched more intelligence officers and communications trackers to apprehend the perpetrators," he said.

Another source, from the National Police's Gegana bomb squad, said the bombs found at the Bunda Maria Convent and at one of the Klaten locations bore the hallmarks of an Islamic militant group that was the subject of a counterterrorism crackdown at the start of the year.

"We're very sure that these bombs were part of a terrorist plot," he said. "The composition of the bombs resembles those found in the militant training camp in Aceh."

He said both used aluminum detonators of the same size and shape, tipped with white cement. The group was believed to have been plotting several Mumbai-type attacks on Indonesian targets.

One of its alleged financiers was Abu Bakar Bashir, the firebrand cleric widely believed to be the spiritual leader of the Southeast Asian terror group Jemaah Islamiyah.

National Police spokesman Insp. Gen. Iskandar Hasan said the discovery of the bombs had prompted police across the country to beef up security at churches and hotels in the lead-up to Christmas. "In my opinion, whoever the perpetrators are, they have the capability and they want to show that they exist," he said.

A series of coordinated church bombings on Christmas Eve in 2000 killed 18 people and injured many more. In Jakarta alone, five churches, including the Jakarta Cathedral – the nation's biggest – were targeted. Bashir was tried over those bombings in 2003, but acquitted.