Nigeria ? Militants holding nine foreigners hostage launched attacks Monday on a pipeline and a boat in Nigeria’s swampy delta region, vowing to spread their campaign across the petroleum-rich south from where most of the African oil giant’s crude is pumped.

Attacks on oil installations in recent days by the Movement for the Emancipation of the Niger Delta have now cut about 20 percent of daily oil output in Nigeria, an OPEC member and Africa’s leading producer of crude.

The latest violence didn’t cause further production cuts but helped send oil prices higher on international markets.

Nigeria is the United States’ fifth-largest supplier, usually exporting 2.5 million barrels daily.

There were no reported casualties in the attacks Monday on a Shell-oil operated oil pipeline switching station and a boat the militants claimed housed Nigerian military personnel. “Both were destroyed with explosives,” the militant group said in an e-mailed statement.