Burkina Faso's military vowed to install a unity government after tightening its control over the west African nation, firing tear gas and shots in the air to disperse protesters denouncing an army power grab.

Troops moved into Place de la Nation in the capital Ouagadougou and took over the national television headquarters in a show of force, despite calls by the international community and protesters for a return to civilian rule.

Threatened with economic sanctions, the military pledged to put in place a transition government formed by "broad consensus".

The army has stepped into the power vacuum left by president Blaise Compaore, who was forced to resign in the wake of violent street demonstrations over his 27-year-rule that some have likened to the Arab Spring.

But the military said it was acting only with the interests of the nation at heart and that "power does not interest us".

"What is currently at stake is more than self interest," it said in a statement issued after Isaac Zida -- the man it named as interim chief -- met opposition leaders.

UN envoy for West Africa Mohamed Ibn Chambas said he had joined African leaders in pressing the country's military top brass to hand power back to civilians.

If the army refuses, "the consequences are pretty clear", he said. "We want to avoid having to impose sanctions on Burkina Faso."

There were similar calls from the United States and European Union.

Hundreds of thousands of protesters, furious at plans to extend Compaore's rule in the impoverished landlocked country, had massed on the streets of Ouagadougou on Thursday, some going on a rampage and setting the parliament and other public buildings ablaze.

'Four presidents in three days'

Under Burkina Faso's constitution, the speaker of parliament was supposed to step in as interim head of state following the president's resignation.

But the army instead named Zida, the second-in-command of the presidential guard, as head of the transitional authority.

Zida, 49, beat out an earlier claim to the job by army chief Nabere Honore Traore, winning the military's endorsement on Saturday.

He said he was appointed to ensure a "smooth democratic transition" and promised to consult with the political opposition and civil leaders.

The army reiterated that stance after Zida met opposition leaders, who, along with civil society leaders, had called Sunday's rally in protest at a military takeover.

Several thousand people answered the call, carrying banners bearing the slogans: "The soldiers have stolen our revolution", "Zida get out!" and "Zida is Judas."

Some protesters also headed to the national television headquarters where two opposition leaders made separate attempts to go on air to declare themselves interim chief.

Former defence minister Kouame Lougue -- whose name was chanted by thousands in the streets following Compaore's downfall -- told AFP: "The people have nominated me. I came to answer their call."

But the technicians walked out, interrupting transmission, also foiling a bid by Saran Sereme, a former member of the ruling party, to make her claim as leader of the transition.

"Compaore stayed 27 years, but that's no excuse to have four presidents in three days," said one bemused local in a tweet.

One person was killed close to the television headquarters where soldiers fired shots in the air to disperse protesters. The army said the victim was likely struck by a stray bullet.

Opposition figures have said around 30 people have been killed in a week of violent protests. Hospital sources told AFP that there had been at least six deaths, including two by gunshot wounds.

Bitter disillusionment

urkina Faso -- known as Upper Volta in its era as a French colony before becoming independent in 1960 and changing its name in 1984 -- faces its worst crisis since a wave of unrest three years ago.

From March to June 2011, a spate of army mutinies swept the country, alongside public protests over high food prices, unemployment and the looting of property by troops.

Compaore was only 36 when he seized power in a 1987 coup in which his former friend and one of Africa's most loved leaders, Thomas Sankara, was ousted and assassinated.

Sankara's widow said this week's uprising has "rehabilitated" her husband's memory.

"Dear compatriots, you have brought a victory without precedent with this popular insurrection," she said in a statement to protesters from her home in southern France.

Like several sub-Saharan African leaders Compaore clung to power for the following decades and was re-elected president four times since 1991.

The uprising that finally forced him out was sparked by plans to change the constitution to allow him to stand yet again for elections next year.

His legacy is one of grinding poverty for most of the country, which languishes at 181 out of 187 countries on the UN Human Development Index.

Compaore and his wife have taken refuge in neighbouring Ivory Coast where they are being put up in a luxury government mansion in the capital Yamoussoukro.