A second military officer appears to have taken power in Burkina Faso, a third leader for the West African state in 24 hours.
Colonel Isaac Zida said he had assumed the powers of head of state, and called on the international community to recognise his authority.
Earlier, army chief General Honore Traore said he had taken over.
President Blaise Compaore stood down after 27 years in power amid political unrest on the streets of the capital.
He fled the country and has now arrived in Yamoussoukro, the capital of neighbouring Ivory Coast.
A violent Thursday saw protesters set fire to parliament and government buildings in the Burkinabe capital Ouagadougou.
At least three people were killed, though opposition leaders said dozens had died.
But on Friday crowds danced and cheered in the streets after Mr Compaore's resignation was confirmed.
His fall was prompted by an attempt to amend the constitution and extend his long hold on the presidency.
Under the country's constitution, the president of the Senate should take over after the national president resigns, with elections taking place between 60 and 90 days afterwards.
However, in the hours after Mr Compaore's resignation Gen Traore told reporters he would assume the presidency until elections were called.
Gen Traore's claim to power was later challenged by Col Zida, who made a national address early on Saturday.
He saluted the protesters and offered his condolences for the loss of life, before announcing that the army had taken power "to prevent a state of anarchy that would be detrimental to the goal of democratic change".
Col Zida called for a peaceful transition, adding: "I will assume the duties of head of this transition and head of state to guarantee the continuity of the state."
There has been no report of on Gen Traore's whereabouts or his reaction to Col Zida's declaration.
At the scene: Laeila Adjovi, BBC Afrique, Ouagadougou
Confusion remains in Burkina Faso on who is going to lead the country to the next presidential election.
In Ouagadougou streets are filled with the usual traffic of motorbikes and taxis, but the main market is closed, and some shops have not reopened. The airport is not functioning, and the country's borders are closed. It seems like the "land of upright men" is holding its breath.
Army chiefs are to meet later today and many hope the definitive name of the head of transition will finally come out of their session. Some talks are taking place amongst the opposition, but no-one has come forward to lead the transition.
Some observers say that is because the leader of the transition won't be a candidate in the next elections, so it is more likely that an army chief fills the power vacuum.
According to Francis Sanon, who protested near the parliament on Thursday: "This is all nonsense. It is us, the people, who overthrew Blaise Compaore, not the army. We are going to watch what they are doing, and if we don't agree with the new leader, we will be back out on the street."