A man was allegedly robbed at knifepoint as he jogged along Lake Burley Griffin yesterday afternoon. 

The 26-year-old victim was running along the lake bike path parallel to Lawson Crescent in Acton at about 5.40pm when he was confronted by a man.

Police say the victim was pushed against the wall of an underpass while the offender held an object, believed to be a knife, against his neck, demanding he hand over his wallet and phone.

After the victim handed over a sum of cash and an identification card, the offender became agitated and struck him a number of times in the head.

He fought back and the offender fled towards the National Museum.

The offender is described as being Caucasian in appearance, around 180cm tall and aged between 40 and 60 years. He has long, dirty, grey shoulder-length curly hair with sunken eyes and face. He was wearing black tracksuit pants and a grey zip-up fleece top.

Anyone with information should call 1800 333000 or via the website at www.act.crimestoppers.com.au.