Ex-rebel DR Congo leader Jean-Pierre Bemba will head back to Europe this week after returning to the African country to launch his bid for the presidency in December’s long-delayed elections, as another potential candidate on Saturday remained blocked at the border with Zambia.

Former DRC vice president Bemba arrived in the capital Kinshasa on Wednesday after 11 years abroad — a decade of it behind bars — and on Thursday officially launched his bid to succeed long-serving President Joseph Kabila. Bemba, 55, then arrived in the town of Gemena in his stronghold in the northwest on Saturday.

“Senator Bemba is coming back tomorrow (Sunday) to Kinshasa and immediately leaves for Brussels,” Jacques Djoli, a leader of Bemba’s MLC party, told AFP.

“His next visit to DRC is scheduled for September to take part in work in the Senate and further electoral activities,” Djoli added. Opposition leader Moise Katumbi, meanwhile, was again blocked from returning home as he attempted to get across the border from Zambia, his supporters said.

Earlier, Katumbi supporters had wanted to go to the town of Kasumbalesa, on the Zambian border, to meet him and bring him back so he could submit his election candidacy by the deadline on Wednesday.

He was turned back at the border on Friday although on Saturday he appeared to be poised to finally return with Delly Sesanga, secretary-general of Katumbi’s Ensemble (Together) coalition, telling AFP he was in the process of completing formalities on the Zambian side of the border. But later Saturday, Kamitatu said in a tweet that the Zambian government “had just officially indicated (to Katumbi) the refusal of the Kinshasa authorities to allow him to cross the border to return to his own country“.

In response, DR Congo government spokesman Lambert Mende decried “lies and manipulation” in a tweet, without elaborating.

Katumbi, 53, a wealthy businessman and former governor of the province of Katanga, which lies just across the border from Zambia, has been forbidden from entering the DRC and charged with offences against state security, officials said earlier.

He has been living in self-imposed exile in Belgium since May 2016 after falling out with Kabila who has ruled DRC for 17 years. Katumbi had planned to fly by private jet from Johannesburg to Lubumbashi, the capital of Katanga province, to lodge his application but the city’s mayor refused him entry, while the public prosecutor’s office said Katumbi had been charged with “harming the state’s domestic and external security” and would be arrested if he returned.

Bemba was acquitted of war-crimes charges in June by the International Criminal Court (ICC) in the Hague. Now a senator, he had been in Belgium — the DRC’s former colonial power — since his acquittal. Analysts say Bemba’s return has introduced even more uncertainty into an already volatile election process.

The DRC has never known a peaceful transition of power since it gained independence in 1960 — and some experts fear that the December 23 elections may trigger a bloody conflict. Kabila, 47, has been at the helm since 2001, presiding over a vast mineral-rich country with a reputation for corruption, inequality and unrest.

Supporters said they were making “final adjustments” on Saturday, four days before they must choose their candidate for a December 23 presidential election, a government spokesman said.

“We are not talking about an heir apparent to please foreigners. Our platform’s candidate for the Common Front for Congo (FCC) will be known by August 8,” Lambert Mende told AFP. The FCC is a “grand political electoral coalition” created by the cabinet earlier this year “to provide support for a single candidate” for the elections. It has named Kabila as its “moral authority“.

Kabila had been scheduled to stand down at the end of 2016 after his second elected term, technically the last permitted under the constitution. He has refused to spell out whether he will seek a new term in the vote.