A German oil worker kidnapped by an armed gang in southern Nigeria earlier this month has been released.
Guido Schiffarth was one of 15 people kidnapped by armed groups in the last two weeks. Five remain unaccounted for.
News of the release came after the Nigerian military raided a slum district of Port Harcourt, the main city in the Delta region.
Nigeria’s economically-important oil infrastructure has been the target of a wave of attacks and kidnappings.
Mr Schiffarth, a 62-year-old employed by Bilfinger and Berger, was taken from his car in the southern oil capital Port Harcourt by men who were disguised as soldiers.
“I was well treated and respected,” Mr Schiffarth was quoted as saying by a spokesman for the Rivers State government, news agency Reuters said.
Security officials said the operation marked the start of a campaign ordered by President Olusegun Obasanjo on Tuesday, to break up armed gangs in the region
Oil production cut
Reports from Port Harcourt said there had been sporadic gunfire and soldiers had carried out house to house searches.
“This is the beginning of something bigger to drive all the bandits from the state,” military spokesman Major Sagir Musa told news agency AP. “It will continue. It is ongoing.”
The lack of employment, BBC Nigeria correspondent Alex Last said, has led to many young men joining armed groups.
Some diplomats and officials fear the government’s heavy-handed approach may lead to more violence.
The abductions and attacks on oil facilities have cut Nigeria’s oil production by 25%.
Nigeria is Africa’s biggest oil exporter and the fifth-largest supplier of crude to the United States.
Militant leaders have launched attacks on the oil industry as part of their campaign for local control of oil wealth.