Militants in Nigeria are planning a major wave of attacks and kidnappings in the next few days that could include up to 20 simultaneous bombings across the petroleum-rich south, U.S. diplomats warned Friday.

The warning came in an e-mailed statement sent to American citizens from the U.S. Consulate in Nigeria's main city, Lagos, and a U.S. diplomat confirmed plans for new attacks were believed to be under way.

"The U.S. government has learned that as of late October 2006, a militant Niger Delta group may have finalized its plans for a unified attack against oil facilities in the Niger Delta region," the statement said.

"The attacks allegedly will be carried out sometime during the first week of November and will include 10 to 20 simultaneous bombings of land-based targets and a series of separate attacks on oil installations in which expatriate workers will be taken hostage," the statement said without elaborating.

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A diplomat at the U.S. Consulate in Lagos, speaking on condition of anonymity because he was not authorized to speak to the press about the issue, confirmed the threat was being taken seriously but had no other details.

The news helped push oil prices higher.

Light sweet crude for December delivery rose 47 cents to $58.35 a barrel in electronic trading Friday morning on the New York Mercantile Exchange.

Since the beginning of this year, various militant groups in Nigeria have attacked oil pipelines and taken expatriate oil workers hostage in violence that has cut about 25 percent of the country's usual crude output of about 2.5 million barrels daily.

The militants say they are fighting on behalf of an impoverished population for a greater share of wealth from oil companies and the federal government, which apportions the revenues among Nigeria's 36 states.

Nigeria, Africa's oil giant, is the world's eighth-biggest oil exporter and fifth-biggest source of U.S. oil imports.

The latest kidnapping crisis occurred Thursday, when unidentified gunmen in speedboats seized a Briton and an American from an offshore oil-prospecting vessel belonging to Petroleum Geo-Services, an oil field services company based in Oslo, Norway, that was engaged by oil giant Chevron Corp. to survey the seabed for oil deposits.

Government emissaries made contact with the kidnappers Friday and said both hostages were in good health, said Joshua Benamesia, a security aide to Bayelsa State Gov. Goodluck Jonathan.

"We've made contact, and I can confirm the hostages are well," Benamesia said.

Benamesia said the gunmen claim to have acted on behalf of the Ezetu community living near Chevron's Funiwa platform to back demands for jobs and the building of a local hospital. He gave no further details.

The U.S. Consulate said the latest attack "indicates a continuation of the violence seen since earlier this year in the Niger Delta region."

It also advised U.S. citizens "to exercise caution in their daily activities, and to avoid travel to the Niger Delta region. Americans in the area should limit their travel, particularly at night, and should avoid public venues whenever possible."