Congo protests
President Denis Sassou Nguesso, 71, seeks change in Congo's constitution so as to extend his decades-long rule Anis Mili/Reuters

Clashes broke out when anti-government protesters took to the streets in Congo's capital, Brazzaville ahead of a controversial referendum. At least four demonstrators were killed after security forces opened gunfire on the crowd.

Thousands of protesters were rallying against the proposed change in Congo's constitution that would allow President Denis Sassou Nguesso, 71, to run for a third term in office. Nguesso, who has been ruling the African nation since 1979 except for a brief period of five years, wants to alter the age limit and terms of the constitution so that he can contest the elections in 2016.

Even though the police used tear gas to disperse the crowd, the marchers, who were holding placards reading "Sassaou get out," did not heed the authorities' call. Erecting barricades and burning tyres, the protesters were determined to press ahead with their campaign.

Protesters say at least four people were shot dead by government forces after riot forces were unable to quell the swelling protests. "We insist, and will do everything to see that the constitution is maintained the way it has been," said Guy Parfait Kolelas, a presidential candidate who took part in the demonstrations. Local reports suggest several others are injured, some severely, in the skirmishes.

The government has announced that the referendum to makes changes in the constitution would take place on Sunday, 25 October, while banning all kinds of gatherings leading up to the day. However, the protesters have promised to defy the ban dubbing the protests as "civil disobedience" against the government.

"There were people among the radical opposition who had planned today to march to the presidency. So, it's but logical that order be installed to guarantee the security of citizens," said government spokesperson Thierry Moungalla defending the administration's decision to roll out riot police ahead of the march.

Communications including mobile and internet services were knocked off prior to the rallies. "The symbols of the republic, such as the police headquarters (or) gendarmerie brigades, were targeted... [by the] organised and coordinated insurrection," Congo's Interior Minister Raymond Mboulou told the state-run broadcaster.

At least one police station has been torched by the protesters while most shops and schools remain shut in the capital. Condemning the rise in violence, Sarah Sewall, under-secretary of state for civilian security, democracy and human rights, told reporters: "The United States strongly urges all parties, including both the government and the opposition, to engage in dialogue and to refrain from violent actions that would undermine the hard-won peace that all citizens deserve."