BEIRUT -- Last month's sweeping territorial gains by militants from ISIS in Deir al-Zor province have generated a fierce counter-offensive by locals, organized loosely in "popular resistance" groups that are targeting the ultra-extremists. The Syrian Observatory for Human Rights, an anti-regime group based in Britain, reported Sunday on the uptick in violence against the Islamic State.
It said the militants launched a campaign of arrests in the village of Tayyaneh after its residents killed two members of the group, commonly known as ISIS, in a skirmish, and also issued an ultimatum to residents of seven other villages to leave their homes, because they were "implicated in fighting" the group.
ISIS was responding to the kidnapping of three ISIS members -- a Syrian, an Iraqi and an Egyptian -- by unknown assailants in the village of Swaidan, the Observatory added.
The incidents come a few weeks after ISIS established a foothold in the city of Deir al-Zor, at the expense of its rivals the Nusra Front and Ahrar al-Sham, and swept through a number of villages in the province, many of which lie along the Euphrates River leading to the Iraqi border.
Observers say that the counter-offensive is very different than the seven-month long campaign against ISIS by rebel groups and rival jihadists, which has claimed thousands of lives.
This time around, small, clandestine groups calling themselves "white shrouds" have adopted a low-profile tactic of assassinating ISIS militants and attacking their positions, in contrast to the earlier tactic of well-known Islamist and Free Syrian Army militias leading the fight.
Graffiti in the name of the "white shroud" movement has appeared in Deir al-Zor province and in a similar move, a small group of masked fighters posted a video over the weekend in the name of the Tawhid Squadrons, pledging to fight against ISIS in Deir al-Zor.
The group identified the Syrian regime, its ally Hezbollah and ISIS as its targets, and its rhetoric, like much of the Syrian conflict, is difficult to categorize easily, since it is a mix of nationalism and Islamism.
The group's spokesman said the group represented the "military arm of the Syrian people," and pledged to "purify the land of the occupying Assad regime, and its evil arm, the (Abu Bakr) Baghdadi gang of treacherous ISIS."
He advised the public to stay away from ISIS headquarters and said the group would act like "ghosts above the earth" as they targeted their enemies. This is in line with the most recent tactic of forming small, secretive groups, and not large militias, to fight ISIS.
It named Tunisians, Chechens and other non-Syrian nationals as the focus of its rage, while also "outing" Syrians guilty of treason by allying themselves with ISIS.
A succinct, earlier "message to oppressors" by the group, which emerged in the second half of July, summed up its stance. "Leave our land. There is no place for you among the Syrian people, who rose up against injustice, and not to replace tyrannical rule with another oppressor."
In the last few weeks a string of small-scale, hit-and-run attacks have been reported in more than half a dozen villages in the thinly populated stretch of territory between Deir al-Zor and the border town of Al-Bukamal, where a demonstration by residents against ISIS late last month was dispersed by gunfire.
Observers say the "white shroud" phenomenon represents a simplistic tactic rather than an organized movement, but one that can be copied easily by those who want to battle ISIS.
"These are groups of a handful of men, organized in small cells, and they probably don't have much contact with other groups," said one independent observer, who requested anonymity because of the possibility of retribution by ISIS.
"They carry out a variety of attacks, such as assassinating ISIS leaders or members, either by planting bombs, tossing hand grenades or shooting at a car, or deploying in small attacking squads."
"They obviously are more inclined to target ISIS members who aren't accompanied by security details, and the tactic appears to be catching on."
Some supporters of the movement against ISIS are referring to the actions as a "tribal intifada" although the tribal factor is not the only one involved, observers say.
An anti- ISIS movement was widely reported last week, when members of the Sheaitat tribe, concentrated in three villages between Deir al-Zor and the Iraqi border, rose up against ISIS after several members of the tribe were detained by the militants.
The violence is believed to have claimed the lives of several tribe members and at least nine ISIS members.
Anti-regime media activists posted video footage purporting to show one of the ISIS militants being led away from a small mob after he was captured in battle. Another, more grisly piece of footage shows a captured ISIS militant, missing his right hand, paraded through town in the back of a pickup truck.
A spokesman for the FSA told a pro-opposition television station this weekend that a "white shroud"-style attack had also taken place in the city of Deir al-Zor, against an ISIS convoy.
Activists from both sides of the conflict, meanwhile, have been busy relaying reports of the fighting, and their rage against their enemies, via social media forums.
ISIS supporters have been railing against residents of Deir al-Zor for being too attached to tobacco and hashish, a reference to the recent ISIS actions to clamp down on smoking in areas the militants control.
The observer said ISIS was largely to blame for the counter-offensive because it had violated the non-aggression pacts struck with locals.
When it swept through Deir al-Zor last month, ISIS didn't rely on massive manpower, but rather its fearsome reputation -- for conducting gruesome public summary executions -- and a series of deals worked out in rural villages and towns.
"One of the key points was that ISIS was to remain clear of populated areas, but it appears that they ignored this condition and entered neighborhoods, and arrested people," the observer said.
Referring to areas purported to be under ISIS control in northern and eastern Syria, the observer said: "You can't control a population of 5 or 6 million people with a few thousand fighters unless you adhere to your agreement with them -- otherwise, you'll need fighters everywhere."