U.N. chief Ban Ki-moon Wednesday urged world leaders "not to abandon" the Sahel region, but urged caution amid calls for military intervention to flush out armed Islamist rebels in northern Mali.

"The region needs your attention, your focus. Do not abandon it and regret it later," Ban told a high-level meeting on the sidelines of the U.N. General Assembly.

Mali's government must apply Islamic sharia law before armed Islamist groups who control the north of the country will negotiate, an Islamist official said Saturday.

Alioune Toure, a security chief in the city of Gao held by the Movement for Oneness and Jihad in West Africa (MUJAO), was responding to an offer of talks made late Friday by Mali's interim president, Dioncounda Traore.

France would provide logistical support for any military intervention in northern Mali, which was overrun by Islamist militants this year, Defense Minister Jean-Yves Le Drian said Thursday.

He said the initiative for any such action would come from African states, saying "clearly, that is being developed". A west African regional grouping has been considering sending more than 3,000 troops into northern Mali.

Islamists have destroyed the tomb of a Muslim saint in a northern Mali region under their control, two months after similar incidents in the region brought widespread condemnation, sources said Monday.

"The Islamists on Saturday destroyed the mausoleum of Cheik El-Kebir, 330 kilometres from Gao," a local politician told Agence France Presse on condition of anonymity. "Twelve of them arrived at the site. They demolished the mausoleum with hammers, picks."

Mauritania's president said Wednesday that the killing of nine Mauritanians by soldiers in neighboring Mali last week was an "odious crime", but stressed it had caused no diplomatic rift.

"This odious crime was committed because of the difficult political and security circumstances our brotherly neighbor is experiencing," President Ould Abdel Aziz said, referring to the Islamist takeover of Mali's north.

Mauritania on Monday accused the Malian army of perpetrating a "barbaric massacre" after the shooting in central Mali of 16 unarmed Muslim preachers, including eight Mauritanians.

The Mauritanian government denounced "the cruelty of this unjustifiable collective murder of unarmed, innocent preachers by armed men dressed in the uniform of the regular army", calling the shooting "a barbaric massacre".

At least 16 members of an Islamist sect were killed when Malian soldiers opened fire on their vehicle in the central region of Segou overnight, a government official and police said Sunday.

The incident occurred in the town of Diabali, but it was not immediately clear if the presence of Islamists in the area signified an advance by the jihadists who have controlled northern Mali for five months.

Islamic extremists occupying northern Mali said Sunday they have executed an Algerian diplomat kidnapped five months ago, after an ultimatum given to his government to fulfill their demands expired.

The Movement for Oneness and Jihad in West Africa (MUJAO) said Algerian vice-consul Tahar Touati was executed on Saturday morning, and threatened the three other hostages still in their hands if Algiers does not comply with their demands.

Islamic extremists on Saturday seized the town of Douentza on the frontier of the northern territory they control, and the government-held south, residents told Agence France Presse.

Moussa Dicko, a teacher in the town which lies 170km from Mopti, which is under army control, said the Movement for Oneness and Jihad in West Africa (MUJAO) fighters had entered the town on Saturday morning.

Islamist extremists occupying northern Mali on Wednesday banned all music except the singing of Koranic verses on private radio stations, in line with sharia, the strict Islamic law they are enforcing.

Whether Madonna, Rihanna or Youssou Ndour, all non-Muslim lyrics have been declared Satanic.