Police raid two homes in Sydney's west

Riot police and detectives are searching two properties in Merrylands in relation to an ongoing investigation.

Heavily-armed police are raiding two homes in Sydney's west in relation to an ongoing investigation. (AAP)

Heavily-armed police are raiding two homes in Sydney's west and have blocked a suburban street.

Riot squad police and State Crime Command officers surrounded the homes on Lockwood St at Merrylands on Thursday afternoon.

Police did not specify what the operation was in relation to, only saying it was the result of "ongoing investigation".

Police confirmed the raids were not related to terrorism.