Democratic Republic of Congo opposition leader Moise Katumbi, repeatedly blocked from returning home to contest presidential polls, will try every avenue to get through, his spokesperson said on Sunday.
On Friday and Saturday, Katumbi was refused entry from Zambia as he tried to get home before a deadline on Wednesday to submit his candidacy for presidential polls due December 23.
"It is a violation of the constitution, of the Saint-Sylvestre accord and of two UN Security Council resolutions," Katumbi spokesperson Olivier Kamitatu told AFP.
He is going to take his case "to every forum" possible, Kamitatu added.
The 2016 Saint-Sylvestre agreement negotiated with the opposition allowed President Joseph Kabila to remain in office beyond the end of his second and officially last mandate on December 20 of that year in return for his agreeing to the holding of new, credible elections.
Katumbi's French lawyer Eric Dupond-Moretti said Friday that he would take his client's case "to the UN human rights committee to register this new violation of the fundamental rights of Moise Katumbi and this violation of the democratic process."
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Spokesperson Kamitatu said Katumbi on Sunday was some 150km from the DRC border which he had tried to cross on Friday and Saturday from the Zambian town of Kasumbalesa.
A fresh return attempt "might be part of the strategy," Kamitatu added without elaborating.
Katumbi, 53, a wealthy businessman and former governor of the province of Katanga, has been forbidden from entering the DRC and charged with offences against state security, officials said.
He 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.
"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.
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 December 23 vote.