Royal Dutch Shell has shut its Estuary oil field in Nigeria’s southern delta region as a precautionary measure after an attack from The Movement for the Emancipation of the Niger Delta (Mend), the main rebel group in Nigeria’s oil region.

The militants attacked the oil field near Shell’s Forcados oil export terminal and set it ablaze, Bloomberg reported.

The strike targeted two well clusters in the western Niger River delta.

Shell spokesman Tony Okonedo said that the company had shut production as a precautionary measure while further investigations continued.

On 25 June the rebel group rejected an amnesty proposal from President Umaru Yar’Adua, saying that the offer failed to address key issues. Under the terms, fighters in the Niger River delta have until 4 October 2009 to surrender their weapons, renounce violence and accept rehabilitation to avoid prosecution.

Issues not addressed by the offer include the “genuine, unconditional release” of MEND leader Henry Okah, who is facing trial for treason and gun-running, as well as the demand for locals’ control of resources, the group said.

MEND, which says it’s fighting on behalf of the region’s poor, has stepped up a sabotage campaign against Nigeria’s oil industry since a military offensive against its positions in the delta began last month.

The group said its objective is to destroy Nigeria’s oil infrastructure to force the government to address its political demands, adding that government efforts to deal with individual commanders will fail.