A serial criminal has pleaded guilty to two armed robberies at southside betting venues.

The 35-year-old man, who cannot be named for legal reasons, was due to stand trial in the ACT Supreme Court on Monday.

He instead pleaded guilty to two charges of aggravated robbery in Erindale in 2009 and 2010.

Cleaners at the Erindale Vikings Club were confronted by two masked men about 3.45am in July 2009.

The offender was armed with a gun, knife and a punch-bar, while his accomplice had a knife.

The pair used cable ties to bind the hands of the cleaners and then broke into the club’s many poker machines and took $748.

The robbers fled when another cleaner arrived on the scene.

In 2010, the man and a co-offender stormed the Erindale ACTTAB about 9.40pm on Cox Plate day, the betting agency’s second biggest day of the year, armed with a sawn-off rifle.

The man confronted a security guard and directed customers to stand against a wall.

He then forced his way behind the counter and ordered an employee to open the safe.

The offender put the day’s takings into a bag before fleeing with $46,229.

The jury trial was set down for five days but the man admitted his guilt before matter could start.

He was remanded to reappear for sentence in September.