(Adds hostage's arrival in Rome, paragraph 3) By Estelle Shirbon ABUJA, Jan 18 (Reuters) - Nigerian militants released a sick Italian oil worker who had been in captivity in the remote creeks of the Niger Delta since Dec. 7 but said they would keep three other foreign hostages indefinitely. All four worked for Agip, a unit of Italian energy firm Eni <ENI.MI>. Roberto Dieghi arrived at Rome's Ciampino airport shortly after 7 p.m. (1800 GMT) and television pictures showed him smiling as he left the plane. He was questioned by an Italian magistrate investigating the hijacking, judicial sources said. In December, the militants said Dieghi had blood in his stools and they later said he had other health "issues". "There are no discussions ongoing with regard to the release of the remaining two Italians and one Lebanese still in our custody. They are being held indefinitely," the Movement for the Emancipation of the Niger Delta (MEND) said in a statement. "The eventual release of all hostages in our custody and the possible release of all hostages of Niger Delta origin in Nigerian government hands will not signify an end to our campaign." This stance differed from earlier statements that they would release the hostages only in exchange for four prisoners of delta origin in Nigerian jails -- an impeached state governor, a militant leader from another group and any two others. "We will rather change tactics, desisting from kidnappings and concentrate on acts of sabotage, including bombings, aimed at crippling the oil sector," said MEND. A group which emerged in late 2005, MEND launched a wave of attacks on oil facilities and kidnappings of oil workers in February last year that stopped production of more than 500,000 barrels per day (bpd). The output, a fifth of the production from the world's eighth-biggest exporter of crude, remains shut in. RESOURCE CONTROL MEND says it is fighting for local control over oil assets in the Niger Delta, where five decades of oil extraction have yielded huge revenues for the Nigerian government and Western oil majors but few benefits for impoverished residents. Poverty fuels militancy and crime in the lawless creeks of the delta, a region almost the size of England. Attacks on the oil industry, abductions of oil workers for ransom or for political motives and smuggling of stolen crude oil are common. "The only alternative to our armed campaign against the oil industry is the restoration of the stolen wealth of the Niger Delta people to its rightful owners," MEND said. This is not the first time MEND has announced a change in tactics. Last year, after capturing and releasing dozens of foreign hostages, the group said it was giving up abductions, only to seize the latest four hostages on Dec. 7. The MEND said the release was the result of negotiations with the government of Bayelsa state, where the four men were kidnapped during a raid on an Agip oil export terminal. Dieghi was handed over to a state government delegation at about 1 a.m. Nigerian time (0000 GMT), the militants said. "This release ... had absolutely nothing to do with Roberto Dieghi's poor state of health. The release of Mr Dieghi is an act of goodwill on our part which we hope will be reciprocated by the Nigerian government," the statement said. (Additional reporting by Silvia Aloisi in Rome)
