March 16 (GIN)—Journalists, activists, hip-hop artists and a U.S. diplomat were rounded up by police at a pro-democracy event Sunday in the Democratic Republic of the Congo, sponsored in part by the U.S. government. Security forces charged them with threatening stability, according to a government spokesman.

The diplomat, Kevin Sturr, “was among a group of people believed to be in the process of bringing an attack against state security,” said the DRC’s information minister, Lambert Mende. Sturr, who works with the USAID’s democracy and good governance program in the DRC, was returned to the U.S. Embassy late Sunday night, Mende said Monday.

The activists included members of Burkina Faso’s Balai Citoyen and Senegal’s Y’en a Marre movements. Both have led large-scale protests in recent years against presidents attempting to extend their time in office.

The roundup was an unpleasant surprise for U.S. officials. “This event is one of many activities the U.S. government supports that involve youth and civil society as part of our broader commitment to encourage a range of voices to be heard,” the U.S. Embassy said in a statement.

State Department spokeswoman Jen Psaki complained that U.S. authorities had not been officially informed about why Sturr was detained. “Our ambassador in Kinshasa has raised this at the highest levels with the DRC government,” Psaki said.

Congolese government officials and ruling coalition parties were invited to the event and some attended, the embassy said, describing the youth groups involved as well-regarded and non-partisan.

According to the information minister, the DRC’s intelligence services believed the news conference—billed as an exchange between African civil society organizations—was in fact a project organized by “instructors in insurrection.”

Foreign activists arrested included Fadel Barro, a member of the Senegalese collective of journalists, and members of the hip-hop artists Y’en a Marre movement, which helped organize protests against former President Abdoulaye Wade’s bid for a third term in 2012.

The group had gathered to support Filimbi, a Congolese movement that aims for greater youth participation in politics, when they were rounded up.

Proposed changes in DRC’s electoral law have sparked mass protests against what many view as an attempt by President Joseph Kabila to prolong his time in power. Human Rights Watch reported that at least 40 people were killed in Kinshasa and the eastern city of Goma at protests so far this year.