Gunfire rang out Wednesday at a student demonstration in Kinshasa in a third day of violence over controversial legislation that would extend President Joseph Kabila's term in office, with international concern mounting over the crisis. 

Two shots were heard as dozens of students shouting "Kabila get out!" faced off against a small group of police officers at Kinshasa's university amid sporadic confrontations.

In another neighbourhood, youths destroyed a police vehicle and police fired teargas in an attempt to disperse the protesters.

Protesters oppose a draft law that would enable Kabila, who has been in power for 14 years, to extend his stay in office beyond 2016 when his second term ends.

The fresh violence came as the European Union called for calm and respect for the country's election timetable.

Twenty eight people have been killed since Monday in anti-government protests, according to a local human rights organisation. The authorities put the latest death toll at five.

"This morning we're working all out again because there is a students' protest at the university," police spokesman Israel Mutumbo said. "We are in the process of checking across the city because there are little groups (of possible demonstrators) forming."

Torched town hall

On Tuesday, hundreds of youths torched a town hall in Ngaba, a southern neighbourhood of Kinshasa, while several inmates escaped from a neighbouring prison. Looters also made off with police weapons stored at the site.

At least 20 people were arrested by the army and police as protesters pelted state buildings, public buses and even passing cars with rocks. Soldiers fired in the air to scare off looters who targeted a Chinese-owned store.

The EU on Wednesday urged all parties to show restraint.

"All sides should seek a consensus allowing a return to calm," a statement said, adding that "respect of the electoral calendar as fixed by the constitution is central to the debate."

"The European Union expects publication of a complete calendar including legislative and presidential elections in line with the constitution," it said.

Mass demonstrations

Opposition parties in the biggest, most populous central African country have called for mass demonstrations against the new electoral bill being debated in the Senate.

Speaking from Belgium on Tuesday, DR Congo opposition leader Etienne Tshisekedi called on the Congolese people to force a "dying regime" from power.

Tshisekedi, 82, who is recovering from illness in Europe, has been in opposition since the 1960s, previously taking on the dictator Mobutu Sese Seko as well as Kabila's father Laurent-Desire Kabila.

"The sham regime in Kinshasa is constantly committing irresponsible acts of provocation, plunging the nation into a total impasse that could lead to widespread chaos," he said.

He called on Congolese soldiers and police to "protect citizens and not to obey perverse orders aimed at killing defenceless men and women."

Kabila, now 43, is the son of former president Laurent Kabila who as a rebel leader in 1997 toppled strongman General Joseph-Desire Mobutu.

The younger Kabila first came to power in January 2001 when Kinshasa politicians rushed to make the young soldier head of state after the assassination of his father.

He was returned to office in 2006 in DR Congo's first free election since independence from Belgium in 1960. He began his second and last five-year constitutional term after a hotly disputed vote in 2011.

His opponents believe that Kabila wants to prolong his mandate by making the presidential and parliamentary elections contingent on a new electoral roll, after a census across the vast mineral-rich country set to begin this year.

The government has acknowledged that the census could delay elections due at the end of 2016, but regional analysts and diplomats estimate the process could take up to three years.