MELBOURNE: Police foiled a suicide plot in Australia on Tuesday, arresting four men suspected of links to a Somali Islamic extremist group who were allegedly planning commando-style attacks on at least one army base, senior officers said.

Prime Minister Kevin Rudd said the plot was a "sober reminder" that terrorists are still a threat to Australia, which has drawn the ire of extremist groups for sending troops to join the U.S.-led campaigns in Afghanistan and Iraq.

Some 400 officers from state and national security services took part in 19 pre-dawn raids on properties in Melbourne, Australia's second largest city, and arrested four men.

The raids followed a seven-month surveillance operation against the group, which is allegedly linked to al-Shabaab, a Somali Islamic extremist group, Australian Federal Police Acting Commissioner Tony Negus told reporters.

Members of the cell planned to enter an army base armed with automatic weapons and open fire, Negus said.

"The men's intention was to actually go into the army barracks and to kill as many soldiers as they could before they themselves were killed," Negus said. "This operation has disrupted an alleged terrorist attack that could have claimed many lives."

The suspects were due to appear in court later Tuesday.

The men arrested are Australian citizens ranging in age from 22 to 26, Victoria state police said. Several others were being questioned Tuesday.

The group has been under investigation since January, Negus said.

"This is a sober reminder that the threat of terrorism to Australia continues," Rudd told reporters in the northern city of Cairns.

He said he had been advised that "events today do not at this time warrant any change to our national couterterrorism level, which remains at medium" — the same security warning rating that has been in place in Australia since the Sept. 11, 2001 terrorist attacks in the United States.

The United States has designated al-Shabaab a foreign terrorist organization. The U.S. State Department's annual terrorism report in April said al-Shabaab was providing a safe haven to al-Qaida "elements" wanted for the 1998 bombings of the U.S. embassies in Kenya and Tanzania.