Thirteen Philippine policemen have been sacked and more than 350 others placed under investigation for allegedly cheating in written exams, the police governing body said Sunday.

The National Police Commission said it had invalidated the results of the exams taken last year by 386 people in the southern city of Zamboanga as so many had put exactly the same wrong answers.

The exams were being taken by would-be officers applying to enter the force as well as serving officers seeking promotion.

The cheating was only uncovered recently, and those taking entrance exams had already been commissioned into the force.

Thirteen officers had since been sacked and the rest were under investigation and could also be dismissed, said regional police chief Superintendent Napoleon Estilles.

He did not say how the cheating came to light.

"The termination board found them guilty of... dishonesty," Estilles said.

The controversy highlighted the problems of corruption facing the country's police, who are often derided in the local press as incompetent.

In 2010, a frustrated officer who was sacked from his job over allegations of corruption hijacked a bus carrying Hong Kong tourists.

A bungled police rescue led to the deaths of eight hostages, as well as the gunman.