The mainland's anti-graft agency has confirmed that top intelligence official Ma Jian is under investigation as the country's anti-corruption campaign widens to cover its security and intelligence apparatus. "Vice-minister and member of the party committee of the State Security Ministry Ma Jian has been put under investigation for suspected serious violation of discipline and laws," the Central Commission for Discipline Inspection (CCDI) said in a one-sentence statement posted on its website yesterday. The South China Morning Post reported Ma's detention on corruption charges on Monday. Ma is closely linked to Ling Jihua , the ex-aide of former president Hu Jintao . Ling was detained last month, also on corruption charges. Hours after its statement about the inquiry into Ma, the CCDI announced the detention of Ling's former aide, Huo Ke . Huo was a division head in the General Office of the Communist Party's Central Committee, before being transferred to the China National Tourism Administration. Ma is the highest-ranking national security official to be investigated since the downfall of Zhou Yongkang , the former security tsar. "It is just the beginning and we can expect more state security officers to be netted in the future," said Zhang Ming , a political scientist at Renmin University. There might be a significant personnel reshuffle in the country's intelligence and security arms, he added. Some overseas media reports said the Ma probe was connected to Zhou's case, but sources told the Post the investigation was tied to an inquiry into the top management of the Founder Group, a Peking University-owned technology conglomerate. Ma is believed to be close to the company's chief executive, Li You , who allegedly financed hugely profitable securities trades carried out by one of Ma's relatives. Ma made his last public appearance on December 7 in a visit to Pakistan. Meanwhile, the Politburo Standing Committee said following a meeting it would strengthen the party's centralised and unified leadership, which it called a fundamental political rule. The meeting was chaired by President Xi Jinping . The anti-graft agency's three-day plenum, which concluded on Wednesday, underlined the importance of cracking down on political factions. The People's Daily said in a commentary that corruption and problems within the political system were merging, posing a threat to the party's rule. "[Corrupt officials] have formed networks and engaged in collusion between supervising officials and subordinates, and between officials and businessmen."