Despite appeals notably from the United Nations to respect people's right to protest, troops fired tear gas into churches and bullets in the air to break up gatherings at Catholic masses, in one case arresting 12 altar boys leading a protest in Kinshasa.
Internet links were also down as church and opposition groups defied a ban by authorities to push ahead with the demonstrations.
At least four dead were civilians in the vast, mineral- rich central African country, wracked by tension over delayed elections. A government statement said one policeman had also been killed.
"Two young people were killed in the parish of Saint- Alphonse de Matete," in the east of the country, while another died in the Masina area, police spokesman Colonel Pierrot- Rombaut Mwanamputu said in a televised statement.
Also Read
In Kinshasa, AFP counted at least 15 people hurt and two more in the country's second-biggest city, Lubumbashi.
The protesters were seeking a promise from Kabila that he will not seek to further extend his time in power in the mostly Catholic former Belgian colony.
Kabila has been in power since 2001. Elections to replace him have been delayed and are currently set for December 2018.
Impatience boiled over today, with all the country's main opposition and civil society groups joining in the call for peaceful protests.
One army officer threatened a team of AFP reporters covering the crackdown at St. Michael's church in Kinshasa.
"If you don't clear out of here, I'll order that you be shot at," he said.
"Press, or not, no one is allowed inside. What's more, you have a white man with you -- that's a race that causes us problems."
A journalist for French radio station RFI was briefly detained, AFP reporters saw.
"While we were praying, the soldiers and the police entered the church compound and fired tear gas in the church," he said.
One parishioner who identified herself as Chantal said: "People fell, first-aiders are resuscitating old ladies who have fallen" -- but added the priest carried on saying mass.
At the Notre Dame cathedral in the northern Lingwala district of Kinshasa, security forces deployed tear gas as opposition leader Felix Tshisekedi arrived, AFP reporters said.
After the altar boys dressed in their liturgical robes were detained other protesters started singing for the Virgin Mary to "make Kabila go".
Disclaimer: No Business Standard Journalist was involved in creation of this content