Norwegian oil and gas company Statoil on Saturday confirmed the death of a fourth Norwegian employee at the In Amenas gas plant hostage-taking in Algeria this month.

"Today Statoil received the sad news that one more of our dear and highly valued colleagues who has been missing since the terrorist attack at In Amenas in Algeria is now confirmed dead," the group said in a statement.

French-led troops Saturday seized the airport and a key bridge serving the Islamist stronghold of Gao in a major boost to a 16-day-old offensive to rout Al-Qaida-linked rebels from Mali's sprawling desert north.

The stunning advance came as the extremist Muslim group controlling Gao since June said it was ready for talks to free a 61-year-old French hostage kidnapped in November.

The death of a second Malaysian worker in the Algerian hostage crisis has been confirmed after his body was identified by his dental records and a tattoo, the Malaysian Foreign Ministry said Saturday.

The man, Tan Ping Wee, had been unaccounted for since Islamist militants attacked the In Amenas gas plant in the north African desert on January 16.

U.S. President Barack Obama voiced support Friday for France's military intervention in Mali and vowed to work with French counterpart Francois Hollande to tackle extremism across North Africa.

The two presidents discussed other "shared security concerns," including Algeria, Libya and Syria, during telephone talks, the White House said in a statement.

The African Union is seeking to bolster the strength of the African-led force in Mali, or AFISMA, and has given member states one week to commit troops to the mission, officials said Friday.

"We definitely know, based on the first assumptions... that the force size will have to be significantly augmented," AU peace and security commissioner Ramtane Lamamra told reporters.

French Prime Minister Jean-Marc Ayrault insisted on Friday that the French-led operation against Islamists in Mali was making clear progress and in no danger of getting bogged down.

"There's no risk of a stalemate. France has met and respected the goals it set itself," Ayrault told reporters during a visit to Buenos Aires.

French and Malian troops advanced on the key Islamist stronghold of Gao on Friday after recapturing the northern town of Hombori, as the extremists struck back by bombing a strategic bridge.

The French-led assault against the radical Islamists controlling northern Mali entered its third week with a strong push into the vast semi-arid zone amid rising humanitarian concerns for people in the area facing a dire food crisis.

Islamist fighters have dynamited a strategic bridge near the Niger border on the road to Gao, one of the main towns in northern Mali occupied by extremists, sources said Friday.

"The Islamists dynamited the Tassiga bridge. No one can pass to Niger or come to Gao," said the owner of a transport business, Abdou Maiga.

French warplanes destroyed two Islamist bases in northern Mali as a leading al-Qaida-linked group in the region split Thursday, with the breakaway group saying it wanted talks to end a Paris-led offensive against the militants.

The French bombing raids overnight targeted Ansongo, about 80 kilometers (50 miles) from the town of Gao and extremist bases in the nearby village of the Seyna Sonrai, a Malian military source said on condition of anonymity.

One of the main Islamist groups in Mali split Thursday, with the breakaway faction saying it was ready for talks to end a two-week-old French-led offensive, amid mounting concerns over rights abuses by government troops.

The first of the 6,000 troops pledged by African nations to support France's intervention started heading north, moving closer to the areas a triad of Al-Qaida-linked groups seized in April.