A KNIFE-WIELDING man has killed three children and wounded 12 people aboard a bus in China's latest rampage attack, police say.

A suspect is in custody and officers are trying to confirm him as the assailant in the Monday attack, a government spokeswoman said in the central city of Anyang.

There was no immediate word on a motive.

Those killed were an infant and two boys, although it wasn't known whether the man deliberately targeted young people, Anyang police said in a statement.

Attackers in some previous incidents have targeted children, either out of revenge or blind rage.

Observers have blamed attacks on chronic weaknesses in a mental health system that fails to diagnose and treat those who might be a threat.

Recent attacks include the stabbing of six government family planning workers last month, two of whom died.