The main opposition party in the Democratic Republic of Congo said Friday its secretary general was prevented from leaving the country by authorities and two activists were “kidnapped”.

Jean-Marc Kabund of the Union for Democracy and Social Progress (UDPS) told AFP he was detained Wednesday by immigration services at Ndjili airport in capital Kinshasa, where his passport was confiscated by the Director-General of Migrations (DGM) “without just cause”.

Kabund was headed to Spain for a Socialist International meeting.

His passport was not affected by the country’s ban on non-biometric passports implemented earlier this year, he said, adding that he will file a complaint against DGM on Monday.

The party also accused Congolese authorities of arresting two of its members, James Katshingu, a member of UDPS leader Felix Tshisekedi’s private cabinet and Christian Lumu Lukuasa with the UDPS Youth League.

They were arrested by security forces in Kinshasa’s Limete neighbourhood, where the UDPS headquarters is located, according to Tshisekedi spokesman Abraham Luakabuanga.

Luakabuanga said police had confirmed elements of a report by news site

Contacted by AFP, Congolese authorities said they would comment on the case later Friday.

The UDPS is the main party of an opposition coalition calling for President Joseph Kabila to resign by the end of the year.

The vast African country has seen an outbreak of anti-government demonstrations since Kabila refused to step down in December 2016 on the expiry of his second and final term in office. Elections are now planned for December 2018.

Kabila took office after his father Laurent was assassinated in 2001 at the height of the Second Congo War.