Police found 20 corpses in northern Mexico on Friday after a reported clash between drug gangs, local media reported.

The bodies were scattered in four neighborhoods in the city of Ciudad Madero in Tamaulipas state, and some of them bore signs of torture, according to reports from Mexican broadcasters.

It appeared that the victims were executed in the early hours in the morning. Mexican troops were combing the area for new bodies.

The gruesome discovery came just hours after gunmen murdered 19 people and seriously injured another four in Chihuahua city of Chihuahua, which is also a northern state but far from Tamaulipas.

President Felipe Calderon condemned the killings in a statement, saying that the deaths made him even more determined to fight the nation's drug smugglers. Drug-related violence has claimed more than 20,000 lives since the start of his presidency according to government data.