Nigerian troops have rescued 19 hostages kidnapped by militants in the Niger Delta this month, officials say. Two Americans, two Frenchmen, two Indonesians and a Canadian were freed along with 12 Nigerians in a land, air and sea assault, said officials. Security sources told the BBC the freed hostages were euphoric. The operation was the first successful rescue of foreign captives in the Delta without any of the hostages being killed in the process. It is not clear whether any militants were killed or wounded. The foreigners were captured on 8 November, when gunmen attacked an oil rig belonging to London-based Alfren PLC. The eight Nigerians were seized on an ExxonMobil platform Akwa Ibom state a week later, in an attack claimed by Mend, a military group operating in the Delta. The BBC's Caroline Duffield in Lagos says the rescue operation marks a change in tactics by the Nigerian military, who worked in close co-operation with local contacts to free the captives. Violence in the oil-rich Delta region has subsided since last year. In the past, militants have cut the country's oil production by one-third, causing a spike in global oil prices. The government and many oil militants reached a ceasefire agreement last year in exchange for cash payouts and job training - but a small faction of Mend has resumed the kidnappings. There were always fears that a new generation of militants would emerge which would ignore the ceasefire, says our correspondent. There are also signs the amnesty is faltering, following a firebombing attack on the home of presidential adviser Timi Alaibe last week, she adds. Mend says it is fighting so that more of Nigeria's massive oil wealth is used to benefit the Niger Delta area which produces the oil. But criminal gangs have taken advantage of the region's instability to make money from ransoms paid by oil companies, and stealing oil. Source: BBC