US posts $18m bounty for Nigeria’s Boko Haram, 3 African militants.

The United States posted $18 million in rewards Friday for the capture of four African militants involved in the kidnapping of foreigners and attacks on Western targets.

Some $5 million each was offered for a former member of Nigeria's Boko Haram and two founding leaders of the Movement for Oneness and Jihad in West Africa (MUJAO) based in the Maghreb region.

A fourth reward of $3 million was set for an Egyptian extremist who has plotted against the US, the State Department said.

Khalid al-Barnawi was named as a leader of the Nigeria-based group known as Ansaru that split from Boko Haram in early 2012, the agency's Rewards for Justice program said in a statement.

The group has close ties to Al-Qaeda in the Islamic Maghreb and was behind the kidnapping of seven foreigners in a raid on a construction site in restive northern Nigeria in February 2013.

The seven from Britain, Greece, Lebanon and Italy were later executed by their captors.

Barnawi also reportedly helped plan the May 2011 kidnapping by Ansaru of a British and an Italian engineer, who were both killed 10 months later.

"Ansaru originated as a faction of Boko Haram, has close ties to Al-Qaeda in the Islamic Maghreb, and has sought to target Westerners, including US citizens," the State Department said.

It also named Hamad el-Khairy and Ahmed el-Tilemsi as founding leaders of MUJAO, and former members of AQIM.

Tilemsi took part in the kidnapping of two French nationals in Niamey, Niger in January 2011. The men were later executed in Mali after an attempt by French special forces to rescue them failed.

As a military leader of MUJAO, Tilemsi also aided the abduction of three European aid workers in Algeria from a refugee camp in Tindouf, in October 2011.

MUJAO claimed to be behind that kidnapping — the first time that the group emerged to the fore saying it was an offshoot of AQIM.

The three Europeans were finally released in July 2012 in Mali in exchange for three Islamists held by Mauritania.

While still a member of AQIM, Khairy planned attacks in Mauritania and took part in the December 2008 abduction of UN envoy and Canadian Ambassador Robert Fowler in Niger.

He had also ordered the 2011 kidnapping of the three European aid workers in Algeria, in which two people were also wounded.

Khairy has also claimed responsibility for the April 2012 kidnappings of seven Algerian diplomats in Mali. At least one of the hostages were later killed, and three were freed.

Rewards for Justice also offered $3 million for Egyptian explosives expert Abu Yusuf al-Muhajir, a former member of the Tawhid w'al Jihad Egypt, described as an extremist group active in the Sinai Peninsula from 2004 to 2006.

"Abu Yusuf was involved in attack planning against a variety of targets in Egypt, including