Sydney, Dec 30 (IANS): Australian counter-terrorism police have arrested a man for making online threats against the upcoming New Year's Eve festivities in the Sydney harbour, which are expected to be attended by some one million people, officials said on Friday.

The arrest took place at Sydney International Airport on Thursday after the suspect returned from Britain, Efe news reported.

At the time of the arrest, the police also raided an apartment and a storage facility in Sydney, and seized documents and computer hard disks.

The man, who is expected to appear in court on January 10, has been charged with a Crimes Act offence but not a terrorist offence, Acting Deputy Police Commissioner Frank Mennilli told the media here on Friday.

Authorities believe it to be an isolated case as the man did not have any links to terrorist groups.

Police forces last week arrested seven people who were planning to detonate explosives during Christmas festivities in Sydney.

Australia raised its terror alert in September 2014 and has since tightened security besides adopting a number of counter-terrorism laws to prevent attacks on its soil.