Interim leaders in Burkina Faso have been detained by guards supporting ousted President Blaise Compaore.
President Michel Kafando and Prime Minister Isaac Zida were detained at a cabinet meeting at the presidential palace in the capital, Ouagadougou.
It comes two days after a commission recommended the disbanding of the presidential guard (RSP).
Shots have been fired to disperse hundreds of protesters near the palace, where the detainees remain.
No injuries have been reported but there is said to be an air of panic in the capital with shops shutting early and many people heading home.
Violent mass protests that included setting parliament on fire forced long-serving Mr Compaore out of office in October 2014.
Mr Kafando and Lt Col Zida had been tasked with organising fresh presidential elections next month.
They and other officials were "taken hostage" by the RSP, the head of the transitional parliament, Moumina Cheriff Sy, said in a statement.
Analysis: Thomas Fessy, West Africa correspondent, BBC News
Their captors are soldiers from the elite presidential guard but their intention remains unknown: are they protesting against a plan to dismantle their controversial unit?
Or are they trying to take power less than a month before the first elections are held since former president Compaore fled a popular uprising last year?
Several radio stations have been taken off air and people fear that in the confusion the situation may escalate into violence.
Mr Sy said military chiefs were trying to negotiate the officials' release.
"The RSP's countless disruptions are a serious attack on the republic and its institutions," Mr Sy said.
"I call on all patriots to gather to defend the motherland," he added.
Tensions have been building ahead of the poll scheduled for 11 October.
Members of Mr Compaore's party have been declared ineligible.
Those who supported the ex-president's bid to amend the constitution so he could seek another term are also banned from running.
There has been prolonged friction between the 1,300-strong RSP and Lt Col Zida, a former second-in-command of the group.
Then on Monday, a truth and reconciliation commission released a report calling for the disbanding of the unit amid accusations that it opened fire on unarmed protesters during last year's protests.