Ouagadougou (AFP) - Angry demonstrators went on the rampage in Burkina Faso on Thursday, setting parliament ablaze in an uprising against the regime of long-standing President Blaise Compaore.

The protesters forced the government to scrap a vote on controversial plans to allow Compaore to extend his 27-year rule, with tens of thousands of people joining a mass rally in the capital Ouagadougou calling for the strongman to go.

Hundreds of people stormed parliament and other public buildings including the national television headquarters, ransacking offices and setting fire to cars, despite a heavy police and army presence across the capital Ouagadougou.

The United States and former colonial power France voiced alarm over the unrest gripping the poor west African nation while the UN chief was sending an envoy to help restore calm.

"The army is united with the people," claimed Benewende Sankara, a leading light in the opposition, calling for Compaore to resign to enable peace to be restored.

Army chief Nabere Honore Traore was meeting retired general Kouame Lougue, a former defence minister being touted by the opposition as a replacement for Compaore, to discuss the crisis.

Tens of thousands of protesters massed on the streets of the capital shouting "Lougue in power!"

Hundreds of people had earlier broken through a heavy security cordon and stormed the National Assembly building, before attacking the national television headquarters and moving on the presidential palace.

- Worst crisis since 2011 -

One man was killed in the chaos that erupted just before lawmakers were due to vote on the legislation that would allow Compaore -- who took power in a 1987 coup -- to contest next year's election, AFP correspondents said.

The government, facing its worst crisis since a wave of mutinies shook the country in 2011, later announced it was calling off the vote.

Police and soldiers, out in force after mass rallies earlier this week, failed to stop the onslaught despite using tear gas against the protesters.

Black smoke billowed out of smashed windows at the parliament building, where several offices were ravaged by flames, including the speaker's office, although the main chamber so far appeared to be unscathed.

Several hundred protesters also broke into the headquarters of the national television station RTB, pillaging equipment and smashing cars, correspondents said.

Crowds of people later massed near the presidential palace but were being held back by troops from the presidential guard who fired warning shots into the air.

The ruling party headquarters in the second city of Bobo Dioulasso and the city hall was also torched by protesters, witnesses said.

The United States said it was "deeply concerned" about the crisis and criticised the attempts to alter the constitution, while France appealed for calm and said it "deplored" the violence.

UN Secretary-General Ban Ki-moon dispatched a special envoy to Burkina Faso, with a spokesman saying Ban was "following with great concern the deteriorating security situation in Burkina Faso."

The European Union had urged the government to scrap the legislation, warning it could "jeopardise... stability, equitable development and democratic progress".

- 'Burkina's Black Spring' -

The legislature had been due to examine a proposed amendment that would allow Compaore to run for re-election in November 2015.

Several thousand protesters marched through the capital on Wednesday, the day after street battles erupted during a mass rally by hundreds of thousands against what they branded a constitutional coup by supporters of the 63-year-old strongman.

"October 30 is Burkina Faso's Black Spring, like the Arab Spring," said Emile Pargui Pare of the opposition Movement of People for Progress (MPP).

Government spokesman Alain Edouard Traore had issued a statement Wednesday hailing the "vitality" of Burkina Faso's democracy despite what he termed anti-government "misbehaviour".

Compaore's bid to cling to power has angered many, including young people in a country where 60 percent of the population of almost 17 million is under 25.

Many have spent their entire lives under the leadership of one man and -- with Burkina Faso stagnating at 183rd out of 186 countries on the UN human development index -- many have had enough.

The situation is being closely watched across Africa where at least four heads of state are preparing or considering similar changes to stay in power, from Burundi to Benin and the Democratic Republic of Congo.

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

He has remained in power since, re-elected president four times since 1991 -- to two seven-year and two five-year terms.

Known in colonial times as Upper Volta, the landlocked country became independent from France in 1960 and its name was changed to Burkina Faso ("the land of upright men") in 1984.