A rights group and an opposition lawmaker called on Monday on the government of Democratic Republic of Congo to investigate the late night burial of at least 421 bodies last month.
The government said on Friday that local authorities had buried the corpses overnight on March 19 in the rural commune of Maluku, saying they were dead fetuses and still-born babies as well as unclaimed corpses.
But U.S.-based Human Rights Watch suspects the bodies might belong to people killed in anti-government protests in January or a crackdown on Kinshasa criminals.
At least 40 people died in the violent protests against a proposed law to require a national census before an election - a move that opponents said was an attempt to delay the vote and extend President Joseph Kabila's mandate.
Ida Sawyer, senior researcher for HRW in Congo, said bodies went missing both during the protests as well as in an anti-gang operation in late 2013 and early 2014, in which the group says at least 51 people were killed.
"Further investigations are required to determine if the bodies of those killed in January are among those buried in Maluku," she said.
The political climate in Congo is tense ahead of the presidential election scheduled for late next year when Kabila's mandate is set to expire.
A parliamentarian with the opposition Engagement for Citizenship and Development (ECIDE) party asked for the bodies to be exhumed and for autopsies to be conducted.
"Why bury these people at night? There needs to be an inquiry. This is not a simple affair," Martin Fayulu, told Reuters on Monday.
Human rights workers first became aware of the burial site after residents of Maluku reported a smell and tire tracks near the local cemetery more than two weeks ago.
"The women who work the fields there noticed a foul odor. They discovered the leg of a body," said Dolly Idefo, executive director of Voice for the Voiceless, a Kinshasa-based human rights organization.
There was nothing to mark the burial site, Idefo added.
The government says the bodies were buried individually and not in a mass grave.
Congo's justice minister, Alexis Thambwe, said on Friday the government was prepared to exhume all the corpses should anyone raise the "slightest doubt" about the circumstances of their deaths.
But government spokesman Lambert Mende said on Monday there would be no exhumations, saying that human rights bodies or government officials had no right to make such a request.