Authorities are tightening the leash on police fter riots sparked by alleged police injustice. Several government agencies are saying for the first time that officers will be held to account for abuses of power and use of excessive force in dealing with petitioners. Several central government agencies, including the Communist Party's Central Commission for Discipline Inspection, unveiled two documents yesterday detailing a new code of conduct for police to deal with petitioners. The new documents say officials will be demoted or even sacked if they fail to show up or properly handle a major petition incident or riot, or fail to prevent an issue with major negative social implications. Police risk being demoted or sacked if they are found carrying and using arms improperly. Zhang Huixin , deputy secretary of the commission, promised to investigate whether corruption lay behind violations of disciplinary guidelines on petitioning. Anyone suspected of committing breaches would face prosecution. Aggrieved residents are often forced to turn to higher authorities to have their complaints heard after being repeatedly rejected by lower-level courts and officials. Quoting Zhang Enxi, deputy director of the State Bureau for Letters and Calls, a central government agency that handles petitions, Xinhua said the documents were the first accountability mechanism introduced specifically to target police handling of petitioners. Mr Zhang said the mechanism would help promote a petitioning system based on the rule of law. The move follows at least four large riots against police injustice in fewer than two months. Tens of thousands of people rioted and torched government buildings and the police headquarters in Wengan county, in Guizhou province, late last month over the police investigation into the death of a 17-year-old girl. It was the most serious unrest since the riots in Tibet in March. Police response to community unrest also came under scrutiny on Saturday, when officers in Menglian county, an ethnic-minority border area in Yunnan province near Myanmar, killed two people in a clash over a disagreement between rubber farmers and their buyers. Police have also intensified crackdowns on dissidents, with many petitioners rounded up or harassed in the run-up to the Beijing Olympics, undermining the capital's commitment to a 'people's Olympics'.