Mali’s prime minister was arrested and forced to resign Tuesday by soldiers who orchestrated a military coup in March, bringing fresh turmoil to the West African country, which is also struggling with the seizure of its north by Islamist militants linked to al-Qaeda.

The arrest of Prime Minister Cheick Modibo Diarra late Monday as he was preparing to leave for Paris for medical treatment was followed a few hours later by his forced resignation, along with the dissolution of his government. A solemn-faced Diarra appeared on national television in the early hours of Tuesday.

“Our country is living through a period of crisis. Men and women who are worried about the future of our nation are hoping for peace,” he said. “It’s for this reason that I, Cheick Modibo Diarra, am resigning along with my entire government on this day. . . . I apologize before the entire population of Mali.”

The Associated Press reported that interim president Dioncounda Traore later named Django Sissoko, a veteran public servant, as the new prime minister.

Diarra’s resignation comes as the United States, European countries and regional powers are readying a military force to intervene in Mali’s north, where radical Islamists have created a jihadist haven for al-Qaeda militants and other extremists. A regional alliance has proposed a 3,300-strong force to retake the north, and the U.N. Security Council is weighing whether to approve it.

But Tuesday’s political upheaval is likely to slow plans for such a military strike. U.S. and U.N. officials have cautioned that any intervention should take place after Mali restores constitutional rule and holds democratic elections.

Those moves seem further away now. The junta’s actions underscore its control over the political fortunes of Mali, a vast landlocked nation with large reserves of gold and a predominantly Muslim population.

The army’s spokesman, Bacary Mariko, said Diarra was “not getting along” with the leader of the March coup, Capt. Amadou Sanogo. “It’s the reason why Mali’s army has taken things into their own hands and told Cheick Modibo Diarra to resign for the good of Mali,” Mariko told the AP.

The United States quickly condemned the arrest. State Department spokeswoman Victoria Nuland said Tuesday: “We view this event as a setback for Mali’s transition and its efforts to try to restore constitutional order and democratic government. . . . First and foremost, we need Sanogo and his brothers in arms to stay out of politics because it’s not helping.”

Although the Obama administration is now criticizing Sanogo for plunging Mali into political turmoil, U.S. officials once had high hopes for his career.

Under a program designed to bolster relationships with foreign military officers, Sanogo received extensive training in the United States between 2004 and 2010, attending officer school at Fort Benning, Ga., and a course for intelligence officers at Fort Huachuca, Ariz.

In recent weeks, U.S. officials have pressed Sanogo to step aside and allow elections to take place in April. They also have repeatedly accused him of permitting human rights abuses.

Up in arms in northern Mali

At the same time, the military intervention plan being drafted by the United States, the United Nations, France and Mali’s neighbors was expected to depend heavily on the ill-equipped and poorly led Malian army.That strategy, already shaky, may become unviable as long as Sanogo remains in charge, either officially or behind the scenes.

Soldiers arrested Diarra in his home and took him to a military camp at Kati, on the outskirts of Bamako, the capital, where he was ordered to step down. In recent weeks, Diarra was at odds with Sanogo over military intervention to liberate northern Mali. While Diarra sought international help for such an effort, Sanogo believed that Mali’s military, despite being divided and in disarray, could mount a military strike on its own.

Diarra’s resignation followed a protest he organized last weekend that demanded U.N.-backed military intervention in northern Mali.

Taking advantage of the military coup and subsequent power vacuum in Bamako, the Islamists overran a large swath of northern Mali in March, joining forces with secular Tuareg separatists to seize major towns and effectively divide the nation in two. Then the Islamists pushed out the Tuareg separatists and imposed harsh sharia law across the north.

Craig Whitlock contributed to this story.