Police using anti-firearms powers have raided the western Sydney home of the man accused of supplying the gun a teenage terrorist used to kill police employee Curtis Cheng.

Police said they raided two homes at Merrylands following a suspected threat against a police station in greater Sydney.

One of the homes targeted was that of Talal Alameddine - the man accused of supplying the gun used by Farhad Jabar to kill Mr Cheng.

Key points: Two Merrylands properties raided, one the home of 22-year-old Talal Alameddine

Two Merrylands properties raided, one the home of 22-year-old Talal Alameddine Alameddine is accused of supplying gun which killed police employee Curtis Cheng in October, at hands of Farhad Jabar

Alameddine is accused of supplying gun which killed police employee Curtis Cheng in October, at hands of Farhad Jabar Police say searches carried out under firearms prohibition orders

The home of Alameddine, 22, in Lockwood Street was searched, as well as a nearby property at Blackwood Street.

Both raids started just before 6:00am.

No items of interest were found during the operation but investigations are continuing, NSW Police said in a statement.

"Any threat to police officers or police premises is of major concern and taken extremely seriously, as demonstrated by the operation we undertook today," Assistant Commissioner Mark Jenkins said.

"We will continue to take every precaution necessary to protect our officers and the safety of the wider community, and will respond swiftly to any specific threats that are received."

Police refused to give details about the nature of the threat against police while investigations were ongoing.

Parramatta shooting victim Curtis Cheng (left) and family. ( Supplied: NSW Police )

"Those investigations are continuing and will continue to for time. This may not be the last you see of actions in relation to this investigation," Assistant Commissioner Jenkins said.

"Anyone that would want to try and threaten a police officer or premises can expect that the police will act very, very swiftly and will act with all of the powers available to us to undertake that."

The raids were led by the Middle Eastern Organised Crime Squad and also involved Tactical Operations Unit officers, local police and other specialist units.

Officers said the searches were being conducted under the powers of firearms prohibition orders, which were previously served on a number of men linked to the addresses.

In October, heavily armed officers raided the home in Lockwood Street.

Alameddine was released later that day without charge, but a week later police arrested him again and charged him with supplying the gun that teenage gunman Jabar used to kill Mr Cheng.

Police also raided a house on Blackwood Street, Merrylands, in relation to a threat against police. ( ABC: Luke Rosen )

He was denied bail last month and is due to appear before court in about a week.

Mr Cheng, a long-time police employee, was killed by Jabar outside the New South Wales police headquarters in Parramatta on October 2.

Jabar fired several more shots at officers as they emerged from the building to respond to the incident.

The 15-year-old shooter was killed when police officers returned fire.

During a funeral service in October, Mr Cheng was posthumously awarded a Commissioner's Commendation for outstanding duty.

Some 1,500 people paid their respects to Mr Cheng at the service.

NSW Police described him as a "respected and long-standing police employee".

Police are urging any person who has information about threats to police or to community safety in general to come forward.