"I am grateful to the Nigerian government for their unstinting help and cooperation," Hague said in a statement, without addressing the claim that the U.K. had launched a rescue effort.
In its statement Saturday, Ansaru also blamed the killings on a pledge by Nigerian President Goodluck Jonathan to do "everything possible" to free the hostages. Presidential spokesman Reuben Abati didn't respond to requests for comment Sunday.
While Nigerian authorities have yet to comment publicly about Ansaru's claim, it comes as the nation's security forces remain unable to stop the guerrilla campaign of bombings, shootings and kidnappings across the country's north. The majority of those attacks have been blamed on Boko Haram, an amorphous group that grew out of the remains of a sect that sparked a riot and a security crackdown in Nigeria in 2009 in which about 700 people were killed.
Boko Haram has hit international targets before, including an August 2011 car bombing of the U.N. office in Abuja that killed 25 people and wounded more than 100. An online video also purportedly claims that Boko Haram is currently holding hostage a family of seven French tourists who were abducted from neighboring Cameroon in late February. The group is blamed for killing at least 792 people last year alone, according to an Associated Press count.
Ansaru, which analysts believe split from Boko Haram in January 2012, seems to be focusing much more on Western targets. Analysts say it has closer links to al-Qaida in the Islamic Maghreb and cares more about international issues, as opposed to Boko Haram's largely local grievances. But much remains unknown about Ansaru, which has communicated through short, sometimes muddled online statements.
The hostage killings appear to be the worst in decades targeting foreigners working in Nigeria, an oil-rich nation that's a major crude supplier to the U.S. Most kidnappings in the country's southern oil delta see foreigners released after companies pay ransoms. The latest kidnappings in Nigeria's predominantly Muslim north, however, have seen the hostages killed either by their captors or in military raids to free them, suggesting a new level of danger for expatriate workers there.
The worst violence targeting foreign workers previously in the country's history came during its 1960s civil war. In May 1969, forces with the breakaway Republic of Biafra raided a Nigerian oil field, killing 10 Italian oil workers and a Jordanian. Eighteen other foreign workers taken by Biafran soldiers faced the death penalty, but later were pardoned and released.
Associated Press writers Frances D'Emilio in Rome, Demetris Nellas in Athens, Greece, Sylvia Hui in London and Shehu Saulawa in Bauchi, Nigeria, contributed to this report. Jon Gambrell can be reached at www.twitter.com/jongambrellAP.
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