Four people were detained in Sydney, Australia, in relation to the killing of police worker Curtis Cheng.
More than 200 officers swooped on several properties early on Wednesday, police said, arresting males aged between 16 and 22. A fifth man was held over unrelated fraud charges.
Mr Cheng, 58, was shot dead outside his office on Friday in what police are treating as a terror attack.
Police shot dead his attacker, 15-year-old Farhad Jaber, at the scene.
Jaber, an Australian born in Iran and of Iraqi-Kurdish heritage, is reported to have shouted religious slogans as he killed Mr Cheng, a police accountant.
Australian Prime Minister Malcolm Turnbull has said the attack "appears to have been an act of terrorism".
Read more:
http://www.bbc.co.uk/news/world-australia-34409111
