A man who was kicked in the head, beaten with a stick and robbed has been hospitalised following an assault on him and another two men in an inner-city park area in Melbourne.

The man, believed to be in his 20s, was sitting near the footpath in Birrarung Marr, about 50 metres from St Kilda Road about 4.15am with two friends, when the trio were approached by six men perceived to be of African appearance, Victoria Police spokeswoman Kelly Yates said.

The men, who police also believe were in their 20s, began to kick and hit the man when a stick before punching one of his friends, a 23-year-old Springvale man, in the face.

The offenders stole the victim's phone before running away. The third friend, a 20-year-old man from Noble Park, ran away to seek help and was not assaulted.

The first man was taken to The Alfred hospital in a serious condition, while the Springvale man suffered swelling and abrasions to his face. He was treated by paramedics at the scene.

Anyone with information is asked to phone Crime Stoppers on 1800 333 000, or visit www.crimestoppers.com.au.