BAGHDAD — Scores of bodies have been dumped in Iraq’s canals and palm groves in recent months, reminding terrified residents of the worst days of the country’s sectarian conflict and fueling fears that the stage is being set for another civil war.

In the latest sign of the escalating attacks, the heads of three Sunnis were found Sunday in a market in northern Salaheddin province, while six Shiites were shot dead in the province after being questioned about their religious affiliation, officials said.

The carnage has raised concerns that the Shiite militias that stalked members of the minority Sunni population in the dark days of 2006 and 2007 could be remobilizing, in response to attacks by Sunni extremists.

Members of Asaib Ahl al-Haq, an Iranian-backed Shiite group responsible for thousands of attacks on U.S. forces during the Iraq war, admit they have ramped up targeted killings in response to a cascade of bomb attacks on their neighborhoods.

“We’ve had to be much more active,” said an Asaib Ahl al-Haq commander who goes by the nom de guerre Abu Sajad. “Those who are trying to incite sectarianism, we have to deal with them,” he said, drawing his hand over his throat like a knife.

More than 1,000 people were killed in January in Iraq, according to Agence France-Presse. That was the highest death toll since April 2008.

Iraq’s Shiite-led government is struggling to maintain security as the al-Qaeda splinter group Islamic State of Iraq and Syria, or ISIS, regularly bombs Shiite neighborhoods in Baghdad. The Sunni-dominated group is also battling the army for control of cities in the western province of Anbar.

But analysts say that the absence of a major militant group on the Shiite side had prevented the violence from escalating into all-out war — until now.

“The big dynamic we are dancing around is this move back into civil war, triggered by the Islamic State,” said Toby Dodge, a professor at the London School of Economics. “For a while there wasn’t the second hand to do the clapping, and now there is, and that’s Asaib Ahl al-Haq.”

Formed in 2006, Asaib Ahl al-Haq was responsible for frequent bombings targeting U.S. forces during the Iraq war. Now members say its priority is ISIS.

“You have this computer system, and this whole system was infected with a virus,” said Abu Sajad, referring to ISIS’s prevalence in Iraq. “You have to import something to deal with that. That’s what we are for.”

But he said his militia is not trying to reignite Iraq’s civil war.

“We realize this is a trap and [ISIS] wants us to make a sectarian war,” Abu Sajad said. “When we go targeting, we target specific people.”

His colleague Abu Aya concurred. “The fight will not be public,” he said.

The militiamen said Asaib al-Haq disguises its role by working with the security forces.

“The army isn’t well-versed in street fights, so we go, we help them clean it up,” Abu Sajad said, adding that his fighters often wear military uniforms on operations outside the capital, including in Anbar.

Tough on all militias

Prime Minister Nouri al-Maliki, a Shiite who is accused by Sunnis of oppressing them, has insisted that he is tough on all militias.

“There is no place for Asaib Ahl al-Haq militants within the security forces or armed forces,” government spokesman Ali al-Moussawi said. Any accounts that militias are connected to the security forces are “fabrications,” he said.

However, Michael Knights, an analyst with the Washington Institute, said it was obvious that Shiite militias played a role in the security forces.

“They can bring a very sectarian approach to security, but within the cover of the security forces, which is more worrying than militias that operate openly and illegally,” he said.

The Badr Organization, formed by exiled Iraqis who fought on Iran’s side during the Iran-Iraq war, is particularly active in the security forces’ ranks, Knights said. An Iranian proxy known as Kataib Hezbollah is also increasingly active, he said.

Asaib Ahl al-Haq has been attempting to recast itself as a mainstream political player since the withdrawal of U.S. forces in 2011. It has opened political offices in Baghdad and in Iraq’s predominantly Shiite south.

But it has not abandoned its weapons. Analysts estimate that the number of armed militants in the group ranges from 1,000 to 5,000. Members who were interviewed would not divulge the size of its military wing but said that the group’s active membership — including those involved in community outreach and a burgeoning political wing — is as high as 20,000.

In Sadr City, an impoverished Shiite neighborhood in Baghdad, local council head Kamil Khanjar said growing frustration among youth could drive them to take up arms. Car bombs strike at least every 10 days and unemployment is about 25 percent, he said.

The neighborhood is a stronghold of Shiite cleric Moqtada al-Sadr, whose disbanded militia, the Mahdi Army, was once considered by the Pentagon to be the most dangerous accelerant of sectarian violence in the country. Several residents interviewed said they would not pick up arms again without Sadr’s directive, but they said there is talk of forming “neighborhood protection” groups.

“When the Mahdi Army was active, if any stranger came into the area, we had men on the street,” said Hussam al Sudani, 40, a former militiaman who lives in Sadr City. “Of course, now people are saying, ‘We hope that the Mahdi Army will come back.’ Maybe it will happen, but under a different name.”

“For sure, one spark, and the militias will rise again,” said Ali Khadum al-Assadi, a 27-year-old real estate worker from Sadr City. “Citizens are prepared. If they attack a holy mosque or shrine, or if there are more car bombs, of course we are going to use our weapons.”