The People's Liberation Army has begun a six-month probe into buildings erected without permission, that exceed specifications or are illegally rented out, as part of a broader campaign against corruption, the defence ministry said yesterday. China's armed forces, the world's largest, have become a focus of President Xi Jinping's campaign to root out deeply ingrained graft including bribery, which often takes the form of lavish gifts to officials or extravagant spending of government funds. "Some 'big problems' left over from the past several years continue to exist, and illegality and ill-discipline keeps happening. Chronic problems in the building of barracks have not been totally sorted out," the ministry said. The military vowed to conduct the probe according to the law and to act only on solid evidence. Projects built after the 18th Communist Party congress in 2012 that are found to contravene regulations will be stopped immediately. Projects built before the congress will be given a limited time in which to correct any violations. In an article for Qiushi magazine, Liu Yuan, the political commissar of the PLA General Logistics Department, said the cases of Zhou Yongkang, Xu Caihou, Ling Jihua and Su Rong indicated corruption had spread to the top leadership. The corruption of Xu, who assigned key positions to his allies, had a "fatal" impact on the party and the army, Liu said. Liu called for stringent measures to ensure officials' power was not abused and that strict political discipline was kept. The PLA Daily said there were still "deep-rooted problems" in military infrastructure and barracks, even though the military had been subjected to a relentless anti-corruption campaign over the past two years. The probe into military buildings has already begun at a base in Liaoning province as an experiment, an officer told the newspaper. The experiment will help the PLA's General Logistics Department to draft rules for project approvals, management and the bidding process. The military earlier this year ordered barracks to be built as simply and economically as possible, without using ostentatious or imported building materials. The anti-graft drive in the military comes as Xi steps up efforts to modernise forces that are projecting power across the disputed waters of the East and South China Seas.