The World Wildlife Fund on Monday condemned "death threats"against two of its staff fighting oil exploration in a Democratic Republic of Congonature park just weeks after the park's director was shot."Unidentified callers have threatened the personal safety of two employees workingin the city of Goma," WWF said in a statement.The staff have been involved in efforts to block oil exploration by UK company SocoInternational PLC in nearby Virunga National Park, an 800,000-hectare naturereserve that is among the oldest in Africa and home to rare and endangeredmountain gorillas.Referring to one of the campaigners, a threatening caller said, "We want his head,"according to WWF.The organisation said there had been an increase in intimidating calls, textmessages and notes since the park's director Emmanuel de Merode was shot severaltimes while driving in the region in April. "The callers to WWF said that they had missed killing de Merode, but would not missWWF’s employee," the organisation said. "WWF insists that authorities in DRC doeverything in their power to bring the perpetrators of these threats and de Merode’sattack to justice."There has been mounting worldwide opposition to oil exploration in Virunga, aUNESCO world heritage site that is thought to have the greatest biodiversity on thecontinent.The UK government, Nobel laureate Desmond Tutu, and Virgin's Richard Bransonhave all spoken out against Soco's operations, which have recently involved seismictests in Lake EdwardUNESCO says exploration would breach international conventions on protectingworld heritage, to which DRC is a signatory.But it fears laws could be changed by the Congolese government to allow oilconcessions covering 85 percent of the park's territory to be exploited. Explorationpermits have already been distributed to international firms, including Soco andFrance's Total. Soco's deputy director Roger Cagle told AFP that the firm had been "informed of thenews that two employees of the NGO ... were threatened as a result of theiropposition to oil development."Soco condemns this behaviour and does not tolerate any act of threat orintimidation."Local activists told AFP in October that they received regular threats bordering onharassment.