Mexican president Felipe Calderon has said murders in Mexico dropped 15% to 20% in the first six months of this year compared with the same period of 2011, according to an interview published by the Spanish newspaper El Pais.
Mr Calderon said 2011 had proved "a climactic point" in drug-related killings, though he did not cite specific figures.
"Today, violence related to rivalries between criminals is declining," he said.
"It is higher than when I assumed the presidency, yes, but I insist it is a phenomenon that comes from the brutality and conflicts between cartels, and not precisely from the government's actions."
Mr Calderon claimed in an interview with The Wall Street Journal last month that drug-related killings in Mexico had fallen by roughly 12% in the first five months of this year, although he and his administration have refused to release the actual figures of drug-linked homicides since last September.
The last set of official figures showed such homicides rose 11% to 12,903 during the first nine months of 2011, up from 11,583 in the same period of 2010.
As of the report in September, drug violence had killed more than 47,500 people since Mr Calderon launched an offensive against Mexico's cartels when he took office in December 2006.
Gruesome mass killings continue in parts of northern and western Mexico. In June, members of a drug cartel dumped 49 bodies on a road near the northern industrial city of Monterrey.