The South Korean ministry which handles relations with North Korea has been targeted by hackers in the latest of a series of online attacks on government and corporate websites, an official said Tuesday. The hackers, using Chinese IP addresses, planted malicious software in the email account of a lawmaker\'s aide to try to attack the unification ministry\'s website. Kim Young-Pil, an official at the ministry\'s cyber security centre, told Yonhap news agency the National Intelligence Service alerted the ministry about the attempted attack. The security centre asked the lawmaker\'s aide Monday to change his password or close the email account and the ministry website was not disrupted. Kim said there have been constant attempts to hack into the ministry\'s computer network, but did not elaborate. The South\'s defence ministry last month said it would expand its cyber warfare unit to combat a growing number of Internet attacks from North Korea. The ministry said its cyber command, launched in January last year, would increase the number of personnel from 400 to 500. Isolated, communist North Korea -- which has a tense relationship with its southern neighbour -- reportedly maintains elite hacker units. Seoul has accused Pyongyang of staging cyber attacks on websites of major South Korean government agencies and financial institutions in March this year and in July 2009. Pyongyang rejected those allegations, accusing Seoul of inventing the charges to raise tensions. In May South Korea said a North Korean cyber attack paralysed operations at one of its largest banks.