Mexico drug war deaths over five years now total 47,515
Mexican officials say nearly 13,000 people were killed in violence blamed on organised crime between January and September last year.
This means there have been 47,515 drug-related killings since President Felipe Calderon launched his crackdown on drug traffickers in late 2006.
Officials said the 11% rise in murders was far slower than in previous years.
But with presidential elections in July, violence is set to be a key issue for voters, correspondents say.
On Wednesday, Mexico's Federal Attorney General's office (PGR) released figures showing that 12,903 people had been killed in drug-related violence during the first nine months of 2011.
It was the first time official statistics had been released since January 2011 and came in response to a series of freedom of information requests over several months.
The PGR said that the 11% rise was "a significant decrease" on previous years.
In 2009-2010, murders jumped 70%; 2008-2009 saw a 63% rise and there was a 110% jump in 2007-2008.
But with the 2011 figures running just until September, the overall number of murders could be some 16,000.
The PGR said that the violence was concentrated in a quarter of Mexico's states.Cartel control
There have been improvements in security in some areas, including the border city of Tijuana.
Ciudad Juarez, also on the US-Mexico, continues to be among the most violent municipalities, with 1,206 murders, although this was a sharp drop on the estimated 2,500 killings the year before.
However, experts say the decline in killings may be the result of one cartel exerting overall control rather than specific success by the military or police.
Last year also saw drug violence spread to previously calm areas, including the eastern port city of Veracruz.
The capital, Mexico City, had also been relatively untouched.
But on Wednesday, two decapitated bodies were found inside a burning vehicle outside an upmarket shopping centre in the Santa Fe district of Mexico City.
Two heads were found in front of the car.
The government stresses that Mexico's murder rate is still lower than several nations, including Honduras, Guatemala, Brazil and Venezuela.