UN Prime Minister Antonio Guterres demanded the immediate release of Mali’s President Bah Ndaw and Moctar Diouf, who had been detained by soldiers.
They were sent by soldiers to a military camp near the capital Bamako.
The two have led a caretaker government that came to power after a military coup last August.
They were detained just hours after the government’s remodeling, which was replaced by two army officers who participated in the coup.
Late Monday, Mr. Wang told AFP on the phone that a soldier “came to catch him.” The news agency then said the line was disconnected.
Defense Minister Souleymane Doucouré was also reportedly detained.
The African Union, the Economic Community of West African States (Ekowasu), the EU and the United States have also accused the arrest, saying that Mali’s top politicians must be released without preconditions.
What triggered the recent crisis?
Beverly Ochieng, BBC Monitoring
Ibrahim Bubaka Keita was banished as president last year after weeks of anti-government protests over heightened anxiety, alleged corruption and economic decline.
His dismissal was generally celebrated, but tensions have increased due to the slow pace of change over the last nine months.
A major union strike is in its second week and could cripple the economy.
The caretaker government, which oversees the 18-month transition, has agreed to appoint a new, broader cabinet in the face of these issues and the threat of new protests.
Colonel Sadio Kamala and Colonel Modivo Conne, who were Defense and Security Ministers, respectively, have resigned.
The opposition group M5RFP behind last year’s protests is also furious at the unrewarded ministerial status.
In addition, public confidence in the ability of military leaders to confront the Muslim rebellion that spilled into neighboring Burkina Faso and Niger is waning.
A pre-2012 coup led to extremist Islamists taking advantage of the turmoil and occupying the northern part of the country.
French troops helped regain territory, but attacks continue as rebels take advantage of persistent political unrest in the region.
What will happen next?
Discussions continue at the Katy military camp, where the president and prime minister are detained.
Members of M5RFP also participated in the meeting. The group was critical of the prime minister and may replace him, reports Will Ross, editor of BBC World Service Africa.
A delegation from Ekowasu, who played an important role in establishing a caretaker government, will also visit Bamako.