Nearly 23,000 people have been killed in drug-related violence in Mexico since the launch of a government crackdown on drug gangs at the end of 2006, according to a government report.

The report, leaked to media on Tuesday, said gang violence has continued surging this year, with 3,365 people killed between January and March.

The confidential report, sent to parliamentarians, indicated security forces have been involved in most of the gunbattles of the past three years: 977 fights have been between gangs and security forces, compared to 309 between rival gangs.

The total toll of 22,743 deaths was a rise of more than 7,000 compared with previous official estimates.

The worst-hit regions were in northern areas near the 3,200-kilometre US border.

The government report said Chihuahua state was Mexico's hardest-hit state, with 6,757 people killed.

Drug arrests

More than 121,000 drug suspects have been detained since 2006, according to the document. It gave no figure for how many of those had been convicted.

Fernando Gomez Montt, the interior minister, confirmed in a news conference that new figures had been passed on to legislators but gave no further details.

Violence has spiked since Felipe Calderon, the Mexican president, launched a military crackdown on organised crime when he took office.

The government attributes the increase in violence to gangs lashing back at security forces and infighting among cartels whose leadership has been shaken by the arrest of senior commanders.

The US-backed deployment of more than 40,000 soldiers and federal police across the country has come under increasing criticism from opposition politicians and drug trade experts, who argue the crackdown has led to human rights abuses and done little to stem the flow of narcotics to the US.

In the latest violence, the bodies of six men were found on the side of a road on Tuesday in Cuernavaca, a city near Mexico's capital where authorities say a battle has erupted for leadership of the Beltran Leyva cartel. Its leader was killed in a battle with marines in December.

Police said the six men were tortured, then each shot once in the head.