Bamako - Malian Prime Minister Cheick Modibo Diarra resigned on Tuesday, hours after he was arrested at home by soldiers acting on the orders of former coup leader Amadou Sanogo.
"I, Cheick Modibo Diarra, resign with my government," Diarra said in a brief speech given at the premises of national broadcaster ORTM which aired it.
He gave no reason for his decision.
The resignation plunges further into chaos a country already effectively split in two after armed Islamists linked to al-Qaeda took over the north.
Looking drawn and speaking in solemn tones, Diarra thanked his supporters and expressed the hope that "the new team" would succeed in their task.
His message was delivered hours after a source in his entourage said the prime minister had been arrested by about "20 soldiers who came from Kati", a military barracks outside Bamako and headquarters of the former putschists.
"They said Captain Sanogo sent them to arrest him," he added.
A security source confirmed the information.
Diarra, an astrophysicist who has worked on several Nasa space programmes and served as Microsoft chairperson for Africa, was due to leave for Paris on Monday for a medical check-up.
He cancelled plans to head to the airport when he learned his baggage had been taken off the plane meant to take him to France.
The entourage source said Diarra had recorded a short message which was to be broadcast on state television, but soldiers went to the broadcaster's headquarters to confiscate the tape.
Diarra was named as prime minister in an interim government just weeks after a disastrous March coup that plunged the once stable democracy into a crisis which has seen over half its territory seized by the hardline Islamists.
The 60-year-old is a staunch advocate of plans to send in a west African intervention force to drive out the extremists, who are running the zone according to their brutal interpretation of sharia Islamic law.
Citizens have been flogged, had their hands amputated and been stoned to death as punishments for transgressions.
Such foreign intervention is fiercely opposed by Sanogo.
The previously unknown Sanogo launched a coup on 22 March to oust President Amadou Toumani Toure's government only six weeks before an election marking the end of his time in office.
The move came amid mounting anger by soldiers at their rout by Tuareg separatists, who were slowly making headway in a fresh rebellion to conquer the north and declare independence for a homeland which they call Azawad.
The coup only made it easier for the rebels and their Islamist allies to seize control of an area larger than France.
However the unlikely alliance between the secular separatists and al-Qaeda-linked Islamists quickly crumbled and the Tuareg were driven out of key positions, leaving the vast arid zone in the hands of extremists.
West African nations are pressing hard for the United Nations Security Council to approve a French-backed plan for military intervention. Germany and the United States have offered training and logistical support.
Ivory Coast Foreign Minister Charles Koffi Diby urged the UN Security Council on Monday to approve "in the coming days" an international force to confront extremist groups in northern Mali.
Western powers fear the north could become a new sanctuary for terrorist groups.
European Union foreign ministers Monday approved plans to deploy an EU military training mission in Mali to help the government regain control of the north from the Islamist rebels.
But misgivings are rife over the plan to send in 3 300 west African troops. Many of Mali's neighbours still prefer a negotiated solution and both the UN and US have urged caution.
US ambassador to the UN Susan Rice last week argued that the west African troops would be ill-suited for the desert battle against groups such as Ansar Dine (Defenders of Faith), al-Qaeda in the Islamic Maghreb (Aqim) and its offshoot the Movement for Oneness and Jihad in West Africa (Mujao).
The US wants more details on the capabilities of the force to achieve its objective, the cost of the mission, logistical needs and plan to minimise impacts on civilian security and the humanitarian situation.