Australian police have arrested four people in the southern city of Melbourne after uncovering what they say was a plot to launch an attack.

澳大利亚警方在南部城市墨尔本逮捕四名嫌疑犯，他们被发现在企图某地发动一场攻击。

Hundreds of policemen were involved in pre-dawn raids in Melbourne

The group was preparing a suicide attack on an army base, police said.

More than 400 officers were involved in searching 19 properties across the city before dawn on Tuesday.

The suspects include Australian nationals of Somali and Lebanese descent, and those arrested are due to appear in court later in the day.

Those arrested are aged¹ between 22 and 26, police said.

Suicide plan

"Police believe members of a Melbourne-based group have been undertaking²（从事，保证） planning to carry out a terrorist attack in Australia and allegedly involved in hostilities³ in Somalia," a police statement said.

"The men's intention was to actually go into the army barracks（兵营） and to kill as many soldiers as they could before they themselves were killed," said Tony Negus, acting⁴ chief commissioner⁵ of the Australian Federal Police.

The attack would have been the most serious terrorist attack on Australian soil, he added.

"Members of the group have been actively⁶ seeking a fatwa（法学家的裁决） or religious ruling to justify⁷ a terror attack on Australia," said Mr Negus.

The police said that the raids（突然袭击，搜捕） came after a seven-month operation involving several state and federal agencies.

Homes across several northern Melbourne suburbs（郊外） were among those raided, The Australian reports.

It adds that those arrested are thought to be linked to the Somali-based al-Shabab group, which seeks to overthrow⁸（打倒，推翻） the Somali government and is believed to have links to al-Qaeda.

The BBC's Nick Bryant, in Sydney, says reports suggest electronic surveillance was used to monitor members of the group.

Members of the Melbourne-based cell reportedly travelled to Somalia in recent months to train, The Australian reports.