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

The group was preparing a suicide attack on an army base, police said, cited by the BBC.

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

The suspects are Australian nationals of Somali and Lebanese descent; one man, aged 25, has so far been charged with terrorism offences.

The man from the Glenroy district of Melbourne is due in court later.

Two other men are expected to be charged, while a court has granted police another eight hours to question the fourth man.

A fifth man, who had been detained earlier, is also being questioned about the alleged plot.