Yemeni security forces on Wednesday shot dead the head of the "terror cell" behind the killing of a Frenchman in Sanaa earlier this week, the country's supreme security committee said.

Wael Abdullah Masood al-Waeli, "who supervised the killing of the French citizen," was killed in a clash with security forces in the capital, the committee said.

War veterans, communist leaders and tourists will gather in Vietnam's Dien Bien Phu town Wednesday to mark the 60th anniversary of the country's seminal victory over French colonial forces.

The bloody, 56-day battle in this remote, northwestern valley ended on May 7, 1954, precipitating both the collapse of France's colonial empire and Vietnam's emergence as an independent nation.

A majority of chief editors at French daily Le Monde resigned from their posts on Tuesday amid a conflict with management over editorial reforms.

"A lack of confidence in and communication with editorial management prevents us from fulfilling our roles as chief editors," seven of the newspaper's senior editors said in an internal letter to management.

German Chancellor Angela Merkel said Tuesday it would be a "pity" if the Russian president were to "use" the commemoration of World War II victory for visiting Crimea.

Merkel was responding to a reporter's question about media reports that Vladimir Putin could attend a May 9 military parade in his first visit to the peninsula since Russia annexed the territory in March.

Francois Hollande marked the second anniversary of his election on the defensive on Tuesday, vowing to speed up reforms as he struggles with the worst approval ratings of any modern French leader.

With the latest polls showing him again plumbing record lows in popularity, the embattled Socialist president took to the airwaves for an hour-long interview to champion his record.

French troops had to call for air backup to fight off an assault by well-armed militants in the Central African Republic on Monday in clashes that left several gunmen dead, the military chief of staff in Paris said.

Around 40 heavily-armed militants riding motorcycles and pick-up trucks attacked the French peacekeepers on a road leading to the village of Boguila in the northwest of the strife-torn country, a spokesman told AFP.

Progressive Socialist Party chief Walid Jumblat has reportedly asked Christian political leaders to stop Maronite Patriarch Beshara al-Rahi from visiting the Holy Land despite the insistence of the cardinal that he was backing the Palestinian cause.

Al-Liwaa newspaper said Tuesday that Jumblat made the appeal during the national dialogue session that was chaired by President Michel Suleiman at Baabda Palace a day earlier.

French President Francois Hollande on Monday condemned "in the strongest terms the cowardly attack" in Sanaa, Yemen, that left one Frenchman dead and two others injured.

"In liaison with Yemen's authorities, the state will use all its powers to shine a light on circumstances of this odious act so that its authors are rapidly identified," said the president in a statement.

Maronite Patriarch Beshara al-Rahi celebrated mass at the Roman Catholic pilgrimage site of Lourdes in France on Sunday on the occasion of the international pilgrimage of the Order of Malta.

The Order of Malta’s members and volunteers from all over the world travel each year during the first weekend of May to Lourdes.

A Spanish court on Saturday remanded in custody a French-Algerian man suspected of fighting for terror groups linked to al-Qaida in Syria before he is extradited to France.

Spanish officers with the help of French police seized Abdelmalek Tanem, 24, in the southern city of Almeria on Wednesday.