Felipe Calderón, Mexico’s president, on Monday replaced the man who has been heading the government’s war on drugs, in a move that could lead to an escalation in the bloody battle against criminal gangs.

Mr Calderón said he had accepted the resignation of Eduardo Medina Mora, who has held the post of attorney-general since the administration came to power in December 2006.

The war against drug cartels, deploying thousands of troops and federal police, was launched as a key element of Mr Calderón’s presidency. He has been calling on the Obama administration to contribute additional funds to help fight illegal activity along Mexico’s 2,000-mile border with the US.

Since he became president, 13,000 people are believed to have died in the conflict, according to local media reports. Those killed were mostly criminals, but also include soldiers, police officers and innocent bystanders.

The departure of Mr Medina Mora could mean a bigger role in the drugs war for Genaro García Luna, minister of public security. The two men have often appeared to be at odds, with Mr García Luna favouring a tougher approach despite criticism that his tactics often show scant regard for human rights.

Mr Medina Mora’s successor is Arturo Chávez, a former attorney-general of the state of Chihuahua, one of the hotspots in the drugs war. Last week 18 young men were lined up and shot dead at a drug rehabilitation centre in Ciudad Juárez, the state’s largest city.

Mr Medina Mora, who used to head Cisen, the national intelligence agency, has presided over record drug hauls and the extradition of gangsters to the US.

Mr Calderón said Mr Medina Mora would be given a diplomatic post. Political sources say he will soon be appointed ambassador to the UK.

As part of a mid-term cabinet reshuffle, Mr Calderón also replaced Jesus Reyes Heroles, director-general of Pemex. Declining production and exports at the state oil monopoly are putting a severe strain on the government’s finances.

Mr Reyes Heroles will be succeeded by Juan José Suárez Coppel, a former chief financial officer of Pemex who has spent most of the past three years at Modelo, Mexico’s leading brewer. Mr Suárez Coppel, a former senior member of the finance ministry team, is regarded as a close ally of Agustín Carstens, the current minister.

Alberto Cárdenas was replaced as agriculture minister by Francisco Javier Mayorga, a former holder of the post and a prominent agro-industrialist.