Philippine police killed 11 suspected drug dealers during operations during the weekend, police said on Monday, adding to a surge of drug-related killings since Rodrigo Duterte swept an election last month on promises to wipe out crime.

Duterte's single-issue campaign of tackling illegal drugs and other crime within six months, and his staunch advocacy of extrajudicial killings, struck a chord with Filipino voters. However, rights groups have rebuked him over concerns that, as president, he would live up to his nickname of "the punisher".

The more than 40 drug suspects killed since Duterte's May 9 election victory compares with the 39 deaths recorded in the four months before it, said National Police spokesman Wilben Mayor.