Abuja - Gunmen attacked Nigeria's main anti-corruption taskforce on Wednesday and left behind a death threat for a top investigator, the Economic and Financial Crimes Commission said in a statement. The attack on the Abuja base of the organisation which seeks to combat the oil-rich country's rampant graft comes just weeks after unidentified assailants shot and injured another investigator in Port Harcourt, in southeast Nigeria. "The group of heavily armed bandits invaded the office at about 05:00 and began shooting into the premises, damaging vehicles," the commission's head of media, Wilson Uwujaren, said in a statement. "However, the attack was repelled by guards on duty.""A white envelope dropped by the fleeing attackers was found to contain a death threat addressed to Ishaku Sharu, a senior investigator with the Commission... who heads the foreign exchange malpractices fraud section."Sharu is currently involved in an investigation into "several politically exposed persons and retired military brass", it added.A police investigation is underway.Images released by the commission showed a Toyota pickup truck peppered with large bullet holes.The anti-graft agency has led several high-profile probes in recent years, including one against former oil minister Diezani Alison-Madueke which led to the confiscation last week of her $37m luxury apartment complex in the commercial capital of Lagos.The commission famously daubs the words "Under investigation by the EFCC" in red paint on the homes of those facing the attention of its investigators.President Muhammadu Buhari was elected two years ago vowing to stop the plunder of state funds by corrupt politicians and public officials in the country of 190 million people.The main opposition party, however, has accused him of conducting a political witch-hunt, since many of those arrested and charged were opposition party members or served in the previous administration.