Protests against Burundi's president resumed on Monday, with police also out in force after a weekend marked by more deadly violence in the crisis-hit central African nation, witnesses said.

Members of the security forces took up positions in and around several tense neighborhoods, sealing off roads and preventing any large-scale demonstrations against President Pierre Nkurunziza's controversial bid to stand for a third consecutive term, AFP reporters said.

In Cibitoke, a district of the capital that has been at the heart of the protest movement, several hundred youth were able to throw up barricades and were singing and chanting slogans. The areas of Musaga and Kinanira, meanwhile, were packed with police.

Activists and opposition leaders had called for street protests to be stepped up, after three people died and 40 others were wounded in a grenade attack on Friday evening and after the leader of a small opposition party, Zedi Feruzi, was gunned down along with a bodyguard in the capital on Saturday.

"We started blocking the road at 4am because of the assassination," said Cadet, a 32-year-old teacher and protestor in Cibitoke.

The influential Catholic Church, which is also opposed to Nkurunziza, has meanwhile called for a 24 hour break in protests until Tuesday.

Burundi's crisis, which began in late April after the ruling party nominated Nkurunziza to stand again in the June 26 presidential election, deepened earlier this month when a top general staged a failed coup attempt.

Parliamentary polls, initially set to take place on Tuesday, have been postponed to June 5.

Opposition and rights groups say that Nkurunziza's bid for a third five-year term violates the constitution as well as the terms of a peace deal that ended a 13-year civil war in 2006.

That conflict, marked by brutal ethnic violence between the country's ethnic Hutu and Tutsi communities, left hundreds of thousands dead, and there are fears the latest unrest could plunge the small, landlocked and impoverished nation back into widespread conflict.

Nkurunziza, a former rebel leader and born-again Christian, argues that his first term did not count as he was elected by parliament, not directly by the people.

He has so far resisted the protests and international pressure and intends to maintain his bid for a third term, for which he also has strong support in rural areas and among sections of the Hutu majority.

Refugees continue to flee the violence, however, most to neighboring Tanzania, where over 50,000 people are struggling to survive in dire conditions on the shores of Lake Tanganyika.

Cholera has broken out in squalid camps, where at least 31 people have died among a total of over 3,000 cases of the disease, and numbers are growing by up to 400 cases a day, according to the U.N. refugee agency.