A 21-year-old man was in serious condition yesterday after he was stabbed in Waikiki from an unknown assailant who attempted to rob him, authorities said.

Emergency Medical Service personnel took the man to a trauma hospital after the 4:30 a.m. incident on Kaiulani Avenue, said Bryan Cheplic, Emergency Services Department spokesman.

Police said that the man was found seated at a table in a Burger King restaurant bleeding after being confronted by an unknown man who stabbed him.

The stabbing occurred a few blocks away, police said. The assailant was last seen on foot headed toward Kapili Street.