DOUMA, Syria — Protesters in Syria held a sit-in Wednesday demanding justice for four activists who were forcibly disappeared in 2013 and whose fate remains one of the most haunting mysteries of the country’s 13-year civil war.

On Dec. 9, 2013, gunmen stormed the Violation Documentation Center in Douma, northeast of Damascus, and took Razan Zaitouneh, her husband Wael Hamadeh, Samira Khalil and Nazem Hammadi.

Outspoken and defiantly secular, Zaitouneh was one of Syria’s most well-known human rights activists. Perhaps most dangerously, she was impartial. She chanted in protests against then-President Bashar Assad but was also unflinching in documenting abuses by rebels fighting to oust him.

There has been no sign of life nor proof of death since she and her colleagues were abducted.

Since the ouster of Assad on Dec. 8, protests have erupted across Syria demanding information about thousands of people who were forcibly disappeared under his rule. The new leadership under the Islamist group Hayat Tahrir al-Sham, which orchestrated the offensive to oust Assad, has maintained a neutral stance regarding accusations against various armed groups for forcibly disappearing activists. At the same time, HTS has aligned with activists in their efforts to uncover the truth and seek justice.

“We are gathering here to remind the world of their case,” Yassin Haj Saleh, Khalil’s husband, said Wednesday, adding that the disappearance of activists represents “the deepest wounds” of Syria’s conflict. “This is the first opportunity that allows us to be in Douma, and in front of the place that they were kidnapped from, to speak up about the case, taking advantage of the political change that took place in the country.”

Saleh said they had repeatedly appealed to various armed groups for cooperation in finding the four activists in the years before Assad’s ouster, but were met with silence.

Strong clues had pointed to the Army of Islam, the most powerful rebel faction in Douma at the time, as the perpetrators. The group, made up of religious hard-liners who were pushing out other rebels and imposing strict Shariah rules, long denied involvement. An Army of Islam official, Hamza Bayraqdar, told The Associated Press in 2018 they brought Zaitouneh to Douma to protect her from the Assad government.

The Army of Islam repeatedly blamed the Assad government, along with the Nusra Front — an al-Qaida-linked group originally founded by the current HTS leader — for his wife’s disappearance, Saleh said.

Zaitouneh was a prominent human rights lawyer and founder of the Violation Documentation Center. She also helped organize networks of activists like the Local Coordination Committees, an umbrella network made up of activists who organized protests as part of the Syrian uprising. Her work earned her international recognition.