MEXICO CITY, Apr 24 (Reuters) At least 35 people were killed over the weekend in Mexico, according to local officials, amid a widespread surge in drug gang violence that has driven murders to a level not seen since 2011. In Sinaloa state, 12 people were killed in different incidents since the early hours yesterday, according to local officials. Battles between gangs have increased in the area following the arrest last year of Sinaloa cartel boss Joaquin "El Chapo" Guzman, who was extradited in January to the United States. Nine people were killed in what prosecutors said yesterday was a gun battle between rival drug gangs in the mountains of Mexico's west coast state of Michoacan. The shootout took place Saturday in an isolated village of the municipality of Churumuco, which borders on Guerrero state, where eight bodies were found on the main street and another in the nearby sierra, the state prosecutor's office said in a statement. In January 2014, the federal government effectively took over control of Michoacan for more than a year in a bid to curb violence between drug gangs and community militias that had risen up to fight extortion and kidnappings. The region, especially Guerrero state, is the site of the worst violence in Mexico as gangs battle over fields of opium poppies, which are used to make heroin. A surge in US demand for heroin has fed the violence. Eight bodies were found in different sites around Guerrero yesterday while another six bodies were found in Veracruz state on the Gulf of Mexico, according to local officials. Violence in Mexico has risen to its worst since 2011. In March, there were 2020 recorded murders, the highest for any month since June 2011, according to government data. President Enrique Pena Nieto is facing rising criticism over his handling of the spike in bloodshed. Murders had fallen from their 2011 peak but killings began climbing again during the last two years. Guerrero is the bloodiest state while Michoacan, Sinaloa and Veracruz are in the top six states for firearms murders. REUTERS SHS PM0931