A NSW Police forensic officer at the house that police raided in Merrylands on Thursday. Credit:Peter Rae The charge relates to him travelling to the Syrian battleground in 2013 in a trip that was well-documented in court recently. Hamdi Alqudsi was recently sentenced to a minimum six years in prison for recruiting seven men, including Biber, and facilitating their entry into Syria to fight for terrorist group Jabhat al-Nusra. Fairfax Media revealed earlier this year that Mr Biber had returned to Australia after disappearing from his family's Merrylands home in July 2013. Since returning, he had been posting inflammatory messages on social media, warning of further attacks such as the shooting of police accountant Curtis Cheng and vowing to return to the Middle East if his passport was given back to him.

Mehmet Biber in the backyard of his family's home in Merrylands, in a file picture. Credit:Fairfax Media In one Facebook post, he had encouraged others to leave Australia to fight. "Fearing 'ohh but its so hard, ohh but i dont have enough money, ohh but its dangerous' is not an excuse," he posted in September 2015. Police allege Mr Biber returned to Australia in January 2014 and had been living with his wife in Merrylands. The second male arrested on Thursday is a 17-year-old associate. He tried to leave Australia in January 2015 to travel to Syria but was stopped at the airport.

He also allegedly "played an active role" in encouraging a friend to join him in Syria, police said. Several of their associates were served with Firearm Prohibition Orders on Thursday morning or had their properties searched again if they were already subject to an FPO. NSW Deputy Commissioner Catherine Burn said there were concerns that the 24-year-old man may have learnt how to make improvised explosive devices (IEDs) or to use weaponry while overseas. "Our concern is that if they return to our country then they may use that capability here," she said. Australian Federal Police Assistant Commissioner Neil Gaughan defended the length of time it has taken to lay the charges, saying it had taken a long time to gather evidence.

Gathering evidence from Syria, which has been a war zone for more than five years, was almost impossible and police also had to wait to get electronic evidence from social media companies in America, he said. He said the Commonwealth DPP advised him in October that there would be enough evidence to proceed with charges. "This has been a protracted investigation and a very difficult one," he said. "Evidence collection Syria is extremely difficult based of the fact there are no competent law enforcement officers working in the region." The pair will appear before separate courts on Thursday. A NSW Police spokeswoman said the investigation "has not identified a direct or imminent threat to the community".

On Thursday morning, Prime Minister Malcolm Turnbull told a news conference, "We have to keep on adapting and modernising our tactics, our legislation to deal with these evolving threats. We must not underestimate our enemies. They are agile. They are tech savvy. And we have to move as quickly as them. We have vital legislation that we need to be passed by the Parliament this year. We are reforming the control order regime, so regrettably it can apply to someone as young as 14. "It gives me no joy to say we need to do that but, plainly, we do. We have changes to the law to enable post-sentence detention of terrorist offenders so that if a person is in jail on a serious terrorist offence and they remain a threat to the community, a court can keep them in continuing detention." Mr Turnbull praised "the excellent work our law enforcement and security agencies are doing 24 hours a day, seven days a week, to keep us safe". Loading "It is why my government continues to give these agencies the resources and the legislative powers they need.

"It is why our ADF men and women, our servicemen and women are in the Middle East right now ... seeking to destroy Daesh [Islamic State], to eliminate that terrorist organisation."