BEIRUT — In the northern Syrian town of Harem, militants last week erected a gallows in a public square, saying it was for “frogs,” or traitors.
The town in Idlib province lies within the final enclave controlled by rebels opposed to Syrian President Bashar al-Assad. As government forces mass for what could be a climactic assault there in coming weeks, opposition fighters linked to al-Qaeda are seeking to head off the kind of negotiated surrender that has sealed the fate of other opposition areas.
The gallows, which the militants publicized on their official news website, was “set up to intimidate the traitors that worked on reconciliation agreements to the regime, so that they know that in the end their fate is death,” said an activist in the town, speaking on the condition of anonymity to avoid retaliation. “The purpose of its construction is to strike fear.”
Idlib province is home to almost 3 million people, at least half of them displaced from elsewhere in Syria, including hardened fighters who had previously refused to surrender. The province is also a bastion of al-Qaeda-linked Hayat Tahrir al-Sham, or HTS, which controls about 60 percent of Idlib, with a Turkish-backed coalition of Islamist rebels holding the rest of the territory.
As a possible showdown approaches, the rebels have arrested and tortured people they accuse of conceding defeat, sowing fear in the local population. A doctor was recently pulled from his home at night, witnesses said. A pistachio peddler was arrested as masked men patrolled the street.
“You just keep walking and hope you’ll be okay,” said a witness to the peddler’s detention, speaking on the condition of anonymity out of fear for his safety. “Everyone here is paranoid now. No one wants to talk.”
Monitoring groups and local residents put most of the blame on HTS, formerly known as Jabhat al-Nusra, but say the Turkish-backed fighters have also arrested dozens of people.
Since 2016, government forces have recaptured one rebel stronghold after another, often relying on the “reconciliation” deals to bring an end to the fighting. Those who sign up are usually allowed to stay in their homes, but under government rule. Under previous agreements, those who rejected the deal have been allowed to travel to Idlib province. Now, they are all boxed in.
With the rebels cornered, HTS leader Abu Muhammad al-Julani, in a video late last month, defiantly ruled out any reconciliation with the government. Russia, whose military intervention in Syria three years ago rescued Assad from likely defeat, has described the province’s militants as “festering abscesses” that should be “liquidated.”
The shape of an impending showdown remains unclear, but one seems even more likely after a summit meeting Friday in Tehran involving the leaders of Russia, Turkey and Iran. Turkish President Recep Tayyip Erdogan appealed for a cease-fire in Idlib, warning that any attack could turn into a bloodbath. But Russian President Vladimir Putin and Iranian President Hassan Rouhani, both strong backers of the Assad government, seemed unpersuaded.
Putin called a truce “pointless” and urged the “total annihilation of terrorists in Syria.” In backing the right of Syrian forces to reclaim the province, he said, “We consider it unacceptable when the protection of the civilian population is used as a pretext for letting terrorists avoid a strike.”
As a key supporter of Syria’s rebel groups, Turkey in recent weeks is believed to have intensified pressure on HTS to dissolve and thus forestall a government assault. But experts say the group is likely to fight to the death.
Western governments and aid groups have warned that a military campaign like those that shattered former rebel strongholds in Aleppo and Eastern Ghouta would spell humanitarian catastrophe.
“While we all know . . . that al-Nusra is a terrorist organization listed by the U.N., the others are not and should not pay the price for the Idlib battle,” U.N. special envoy for Syria Staffan de Mistura said Wednesday.
During battles elsewhere in the country, a network of government moles and informants provided the Syrian army with locations of rebel weapon stockpiles and the identities of the people who kept opposition schools and hospitals running. These government agents also encouraged surrender when the time came.
Seeking to extinguish this possibility in Idlib, rebel groups have embarked on their wave of arrests, accusing those they detain of secret communications with government representatives. Many have been taken to secret prisons and tortured, groups documenting the arrests say.
“Although this is certainly why some people have been arrested, the problem now is that it is also being used by al-Nusra to arrest the people who criticize their behavior, or to arrest their opponents,” said Fadel Abdul Ghany, director of the Syrian Network for Human Rights, a monitoring group.
Residents interviewed about the arrests in recent weeks, all speaking on the condition of anonymity, described a climate of paranoia.
“The HTS [has] more than one punishment prison and secret prisons in general, and they’re throwing civilians and activists in them constantly,” said a medic who recounted the arrest of several colleagues. “The strata of doctors is an educated one in this society. They refused extremist and backward thinking,” he said.
Several groups monitoring the situation confirmed the existence of detention facilities across a network of basements and caves. JAN Violations, which records allegations of HTS abuses, said the group had at least five prisons in the province, several of them notorious for torture.
Asim Zedan, the monitoring group’s director, said HTS had installed hundreds of security cameras across Idlib’s provincial capital — also called Idlib — to monitor residents.
There are no comprehensive figures for the number of detentions by rebel groups, because of restrictions on reporting in the area. Naji Abu Huzaifa, a spokesman for the Turkey-backed National Liberation Front, said the group had arrested at least 40 people in recent weeks on suspicion of ties to the Syrian government, but provided no further details.
Almost 10,000 people have been detained by extremist groups during the seven-year conflict, according to the Syrian Network for Human Rights. Many are believed to have been executed.
Residents said it has sometimes been difficult to determine whether a disappearance was linked to politics, extortion or both. Zedan said that several doctors had been kidnapped for large ransoms and that one had been tortured and left by a roadside hours later.
“You can’t know how worrying it is for us to feel caught in the middle of all this fear of an offensive and all this paranoia,” one resident said. “You hear things, bad things, and you know you’re trapped.”
Zakaria Zakaria and Erin Cunningham in Istanbul and Suzan Haidamous in Beirut contributed to this report.