Three men were arrested on Tuesday over an Islamic State group-inspired plot to attack a variety of Sydney targets including police and defense buildings, courts, churches and diplomatic missions, police said.

A 20-year-old suspect had been monitored by police for a year since he returned to Sydney from Lebanon, Australian Federal Police Assistant Commissioner Ian McCartney said. He was known to police in Lebanon.

The suspect is expected to be charged with preparing for a terrorist act and preparing to enter Afghanistan for the purpose of engaging in hostile activities on behalf of the Islamic State group, McCartney said, adding that he was to go to Afghanistan to take part in a separate plot. He could be sentenced to life in prison on each charge if found guilty.

Read more: ABC News