Yao Wei Wu demonstrates what he says happened to him during an encounter with Vancouver police Wednesday morning. (CBC)

The Vancouver Police Department has issued an apology after a man said he was beaten by officers who knocked on the wrong door while investigating a report of a violent domestic dispute.

Plainclothes officers arrived at the right house at 2 a.m. PT Wednesday near Knight and 49th Street in East Vancouver, but they were at the wrong suite, police admitted in a news release Thursday.

Speaking through a translator, Yao Wei Wu told CBC News that as soon as he opened the door the officers pulled him out of the house and beat him.

He was hit multiple times on the back, head and face, said Yao, 44.

He said he did not resist because the men had guns.

It was only after they handcuffed him and asked his name that they appeared to realize they had the wrong man, Yao said.

The officers then called for an ambulance and a Cantonese-speaking police officer.

Yao was taken to hospital where he said doctors found fractured bones around his eye and multiple bruises on his back.

"A full and thorough internal investigation has been launched into the case of an eastside resident who was injured and arrested in a case of mistaken identity," Const. Jana McGuinness said in a news release.

The officers didn't realize there were two separate residences in the house, McGuinness said.

"The man resisted by striking out at the police and trying to slam the door, but the officers persisted in the belief that there may be a woman and child inside who could be in danger."

The man the police were looking for who lived in the other suite in the house was later found and arrested on suspicion of assault, McGuinness said.