Nigeria's main militant group waging an "oil war" declared a 60-day truce on Wednesday after the release of its leader Henry Okah under a government amnesty deal.

"Effective, 0000 hours (2300 gmt) Wednesday July 15, 2009, the Movement for the Emancipation of the Niger Delta (MEND) will be observing a temporary ceasefire for a 60 day period," the group said in a statement.

A day before Okah's release, the MEND took its self-proclaimed "oil war" into Lagos, killing at least five people in the group's first ever attack on Africa's biggest city while sabotaging an oil depot in the harbour area.