Supporters of opposition leader Etienne Tshisekedi have gathered in Kinshasa to mourn the death of a hugely popular figure who has been compared to South African icon Nelson Mandela.

Some fear Tshisekedi’s death could have a destabilizing effect in the Democratic Republic of Congo, a country with a history of foreign intervention, civil war, and leaders who wouldn’t step down. The government has promised Tshisekedi will be buried in state, BBC reported.

Tshisekedi died of a pulmonary embolism at age 84 in Brussels, where he traveled last week for medical checkups, L’iberation reported.

A prominent supporter of democracy, Tshisekedi was supposed to lead a transitional council paving the way for longtime ruler President Joseph Kabila to step down.

Tshisekedi previously spent two years in Brussels getting  medical treatment, returning to DRC in July to a hero’s welcome, BBC reported.

His death comes as the opposition and government were negotiating Kabila’s departure after 16 years in power — a sensitive time for DRC.

Clashes broke out when Kabila announced he planned to stay in power until April 2018. As news spread of Tshisekedi’s death late Wednesday, clashes broke again between a small group of his supporters and police, who fired teargas.

Tshisekedi supporters described him as a monument in his own right, BBC reported:

“This man sacrificed his life, his youth for us all. This man made us open our eyes. He was our icon. This man was an icon for Africa. He was great. We lost a great man,” one woman told the BBC.
Another said his supporters saw him as incorruptible: “He was an historic opponent. (Nelson) Mandela was the best and Tshisekedi comes after.”

Tshisekedi led an opposition coalition demanding that Kabila step down when his mandate expired in December 2016. In a deal brokered by the Catholic Church, he was to oversee a power-sharing deal that would see Kabila leave office in 2017 instead of running for a third term.

Kabila failed to step down when his constitutionally mandated term expired in December, Euro News reported.

DRC has a long history of coups, civil wars, foreign intervention and authoritarian rule. The popular politician’s death could have destabilizing effect.

One of DRC’s first lawyers, Tshisekedi’s political career took off with independence in 1960 when he became an adviser to Prime Minister Patrice Lumumba, BBC reported.

During Tshisekedi’s 57-year political career, he stood up to Mobutu Sese Seko, who ruled then-Zaire from 1965 to 1997 before being overthrown by Rwanda, Uganda and other forces.

Tshisekedi was named prime minister four times in the 1990s as Mobutu contended with the pro-democratic movement in the country, Al Jazeera reported. Tshisekedi never lasted more than a few months as prime minister because he constantly clashed with Sese Seko.

He remained in the opposition when rebel leader Laurent Kabila, father of the current ruler, overthrew Sese Seko. Tshisekedi was arrested twice for election-related violence and sent into internal exile. Laurent ruled from 1997 until his assassination by a bodyguard in 2001.

In a disputed 2011 presidential election, Tshisekedi ran against Joseph Kabila and was runner up. International observers described that election as fraudulent. Ever since then, Tshisekedi’s supporters have referred to him as the “elected president.”

As Tshisekedi’s health deteriorated in the past three years, his son Felix has taken an increasingly prominent role, BBC reported:

The future of the Union for Democracy and Social Progress party is now in the balance. Other, younger, opposition leaders may now find room for maneuver in transition talks that are expected to continue under the auspices of the Congolese bishops’ conference.

Tshisekedi’s son, Felix, could be named prime minister in a future power-sharing government, Al Jazeera reported.