Police were called to the BP Central Service Station on the corner of Plunkett Street and the Princes Highway around 9.15pm on Tuesday.

Police have been told a male, with his face covered, entered the service station, jumped the counter and allegedly threatened the 21-year-old female attendant, demanding money out of the till.

Police allege the man was "armed with an implement" at the time.

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The woman was able to activate a duress alarm, alerting police who attended and secured the scene.

Patrols of the nearby area by South Coast officers failed to find any trace of the alleged robber.

Inquiries are being undertaken by South Coast Police District detectives, who are reviewing CCTV footage.

The man is described as being of a thin build.

Anyone with any information into the incident is urged to contact Nowra Police on 4221 9699 or Crime Stoppers on 1800 333 000.

It is the second alleged armed robbery in the Nowra area in the past few days.

Investigations are also underway after a man was allegedly threatened at knife point and his mobile phone stolen in Bridge Road, Nowra on Sunday (June 19).

Police have been told a 20-year-old man was approached by two unknown people on Bridge Road, near the intersection of the Princes Highway about 7pm and threatened with knives.

The men allegedly stole the man's mobile phone but he refused to hand over his wallet.

The pair fled towards the highway.

Officers attached to South Coast Police District were notified and began investigations into the incident.

Both men are believed to be aged in their early 20s.

One man was described as being of Aboriginal/Torres Strait Islander appearance, short with a solid build, wearing a green shirt/jumper and a cap, and riding a black mountain bike.

The second man was described as being tall with a slim build and brown hair. He was wearing a black hooded jumper and track pants.

As inquiries continue, police are urging anyone with information to come forward and call Nowra Police on 4221 9699 or Crime Stoppers on 1800 333 000.

Information is treated in strict confidence.

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