West African officials arrived in Mali on Tuesday, a country in turmoil after the military arrested the president, prime minister, and defense minister in a “attempted coup,” according to international organizations.

President Bah Ndaw, Prime Minister Moctar Ouane, and Defense Minister Souleymane Doucoure were taken to a military base in Kati, outside of Bamako, on Monday, just hours after two military members were relieved of their duties in a government reshuffle.

The detentions come after the military in August ousted President Ibrahim Boubacar Keita. Ndaw and Ouane were tasked with overseeing an 18-month transition back to civilian rule.

Bamako was calm on Tuesday morning, and the U.S. Embassy said flights were arriving and departing as normal.

Ndaw and Ouane were still detained in Kati, according to Nohoum Togo, a spokesman for the M5-Rfp opposition coalition, and a source in Kati.

A delegation from the main regional decision-making body ECOWAS will visit Bamako on Tuesday, ECOWAS, the United Nations, African Union, European Union and several European countries said in a joint statement. It did not give further details.

ECOWAS played a key role in the formation of an interim government after the August coup.

U.N. Secretary-General Antonio Guterres said late on Monday he was “deeply concerned” by the detention of Mali’s leaders and called for calm and their unconditional release. The U.S. State Department also called for their release.

“Sanctions will be adopted against those who stand in the way of the transition,” said Josep Borrell, High Representative of the EU for Foreign Affairs, on Twitter.

Ndaw and Ouane appear to have moved against the military’s control over a number of key positions, replacing two leaders of the August coup who held positions as ministers of defence and security.

The military was responding to the cabinet reshuffle, according to two sources, though their ultimate objective was unclear.

The situation could escalate instability in the West African region, where al Qaeda and Islamic State-linked groups control large swaths of the desert north and regularly attack the army and civilians.

Mali has been in turmoil since a coup in 2012 sparked an ethnic Tuareg uprising in the north, which was later hijacked by al Qaeda-linked jihadists.

The Islamists were driven back by French forces in 2013, but they have since regrouped and extended their scope into Burkina Faso and Niger.