Eight people were killed Sunday and dozens arrested as security forces in DR Congo cracked down on Catholic worshippers who gathered at churches across the country to demand President Joseph Kabila leave power, a United Nations source said.
The Catholic church had led calls for peaceful protests on Sunday, with all the vast central African country's main opposition and civil society groups expressing support.
A police spokesman denied the security forces had used live ammunition.
Kabila, who has been in power since the 2001 assassination of his father, Laurent Kabila, has not ruled out another presidential run through constitutional changes.
About 50 people were arrested in Kinshasa and seven people were hurt by gunfire, Reuters quoted human rights activist Georges Kapiamba as saying.
Catholic activists had called for protests after Sunday mass, one year after Kabila committed to holding an election to choose his successor by the end of 2017 - an election that has now been delayed until December 2018. He said the other two deaths were being investigated.
Security forces were deployed across the city of 10 million people and witnesses reported to AFP various police operations against protesters at churches.
Rights group Human Rights Watch says two men have been shot dead outside a church in the capital Kinshasa.
Authorities had earlier shut down internet and SMS services and warned that any gathering of more than five people would be dispersed.
"It is for reasons of state security", telecommunications minister Emery Okundji told Reuters.
At the Notre Dame du Congo cathedral in Kinshasa's Lingwala district, where opposition leader Felix Tshisekedi was attending mass, dozens of police and soldiers blocked the path of more than 100 opposition supporters as they prepared to try to march.
About half of the Democratic Republic of Congo's population is Catholic and the church is considered a respected institution by many.
Deadly street demonstrations organized by the opposition since last December have left dozens dead, raising concern the country could plunge into greater political violence.