FILE PHOTO: Katumbi, governor of Democratic Republic of Congo's mineral-rich Katanga province, arrives for a two-day mineral conference in Goma

Lubumbashi - An opposition leader barred from returning to the Democratic Republic of Congo to file a bid to run for the country's presidency vowed on Friday to fight for "real elections".

Moise Katumbi, a wealthy businessman and former governor of the province of Katanga, was forbidden from entering the DRC and charged with offences against state security, officials said.

Katumbi, 53, has been living in self-imposed exile in Belgium since May 2016 after falling out with President Joseph Kabila, who has ruled DRC for 17 years.

He had planned to fly by private jet from Johannesburg to Lubumbashi, the capital of Katanga province, to lodge his application to stand in long-delayed elections in December -- a move that would heap pressure on Kabila.

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.

A journalist with the French radio network RFI said Katumbi instead arrived at the Zambian border post of Kasumbalesa.

Videos posted online by his aides and others showed him on the Zambian side of the border, greeting hundreds of supporters from his car.

"The regime forbids me from landing and barricades the border... My crime? Wanting to enter my country and file my candidacy," Katumbi wrote on Twitter.

"By trying to block me, they want to remove from Congolese their right to real elections. I will fight," he added.

On the Congolese side of the border, security forces responded to protesters who were throwing stones in the air, Congolese police said, adding that a Tanzanian truck driver was slightly injured.

At least two police checkpoints were set up to screen access to Lubumbashi's airport on Friday and the city's main road to Zambia was blocked by a truck, an AFP journalist said.

- Potential arrest -

Katumbi already faced potential arrest after being handed a three-year jail term in absentia in June 2016 in a case of alleged property fraud. 

He has also been accused of hiring mercenaries and for possessing an Italian passport -- Congolese law does not allow dual nationality. He denies the charges in both of those cases.

Another rival of Kabila, former warlord and ex-vice president Jean-Pierre Bemba, 55, returned home this week. He officially launched his bid for the presidency on Thursday.

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.

He was scheduled to stand down at the end of 2016 after his second elected term, technically the last permitted under the constitution.

Kabila has refused to spell out whether he will seek a new term in the vote. 

Angolan President Joao Lourenco met Kabila in the Angolan capital Luanda on Friday and said he had "received guarantees that the electoral process (in the DRC) will proceed in the normal way".

Angolan Foreign Minister Manuel Augusto said he had recommended Kabila to have "respect for the constitution".

Candidates must submit their applications by August 8 and physically be in the country to do so.