A convoy of police cars complete with the riot squad made its way through the Illawarra's northern suburbs under lights and sirens about 9am Wednesday after a member of the public contacted police to report a gunman.

Police were told the man was walking along Lawrence Hargrave Drive and Carter Street. They arrested a man aged in his 50s at a nearby home, shortly afterwards.

Read more: Flinders hairdresser stocked up on steroids for 'bodybuilding comp'

A visibly shocked woman at the Coledale address was heard apologising profusely to police and telling them to "do what you need to do".

Officers seized the weapon, which has been identified as a gel blaster.

The realistic-looking "toy" firearms take ammunition in the form of tiny absorbent balls that swell up into soft gel spheres about 8mm in diameter, once soaked in water. They are legal in some overseas countries and in Queensland, although there they have become subject to increasingly tight restrictions around their storage and use.

They are sold as toys for as little as $150 on overseas and interstate websites.

But under NSW law they are classed as illegal weapons and have resulted in several recent convictions before Illawarra courts.

The man was issued a court attendance notice, to appear in Wollongong Local Court on October 19.

Read more Illawarra court and crime stories here.

The Illawarra Mercury news app is now officially live on both iOS and Android devices. It is available for download in the Apple Store and Google Play.