Sydney, Aug 4 (DPA):  Police swooped on a suspected Islamic terrorist cell Tuesday in Melbourne to forestall a possible suicide attack on an Australian Army barracks, authorities said.

More than 400 police raided 19 homes and picked up people from the country's 16,000-member Somali refugee community in the biggest anti-terrorism operation in three years.

"We believe these men were affiliated with a group called al-Shabaab in Somalia," acting Federal Police Chief Commissioner Tony Negus said.

Members of the group, who have been under surveillance since January, had been observed casing Sydney's Holsworthy Barracks and other military installations.

"We were satisfied the timing was right," Negus said. "Obviously, the primary concern is public safety."

All those arrested or taken in for questioning were Australian citizens of either Somali or Lebanese descent.

Three years ago, a Somali taken in as a refugee and given citizenship returned to his homeland and was killed in fighting in the failed state. Others are believed to have returned to attend al-Shabaab training camps.

The Australian newspaper reported that electronic surveillance suggested the group planned to arm themselves with automatic weapons and storm Holsworthy Barracks, killing as many soldiers as they could before they themselves were killed.

Four years ago, terrorism laws were amended so that prosecutions could be brought against terrorist plotters who may not have fixed on specific targets.