BEIRUT (AP) — Syrian rebels launched an offensive Tuesday against a major government-held city in northwestern Syria, shelling the outskirts and warning residents to remain indoors in the coming days.

The target of the operation is Idlib, a city of some 165,000 people and the provincial capital of a province with the same name. Opposition fighters have controlled the countryside and towns across the province since 2012, but President Bashar Assad's forces have managed to maintain their grip on Idlib city.

The armed opposition factions announced the campaign to capture Idlib in a message posted online Tuesday. They told residents the rebels "are at the walls of Idlib" and "have decided to liberate this good town." The message also asks locals to remain indoors in coming days.

Syrian state TV quoted an unnamed military official as saying that government forces are repelling "attempts by terrorists groups to infiltrate the outskirts" of Idlib. The official said clashes were ongoing, adding that troops inflicted "heavy losses" on the attackers.

Muayad Zurayk, an activist based in Idlib province, said the offensive began Tuesday morning and was being led by several factions including al-Qaida's branch in Syria, the Nusra Front, as well as the ultraconservative Ahrar al-Sham and Jund al-Aqsa groups.

"The rebels have captured five checkpoints so far and are getting close to the gates of Idlib," Zurayk said via Skype. He said rebels are pushing from four directions adding that there were two suicide car bombs in the afternoon that targeted an army base near the city.

He said the operation to capture the city is dubbed "Fatah Army," adding that two opposition fighters have been killed and several others wounded.

The Britain-based Syrian Observatory for Human Rights said rebels are shelling the city, but have yet to try to push into Idlib itself. The Idlib Media Center also said the rebels are targeting government positions on the city's outskirts.

Observatory director Rami Abdurrahman said the opposition groups involved in the operation include the Nusra Front as well as Islamist rebel factions.

Rebels have tried in the past to enter the city of Idlib but did not succeed

More than 220,000 people have been killed since the conflict began in March 2011. The crisis started with largely peaceful protests calling for reforms and escalated into civil war following a brutal government crackdown.

Meanwhile in Damascus, Iraq's visiting foreign minister held talks with Assad that focused on threats facing both countries, including the Islamic State group.

Ibrahim al-Jaafari said they discussed "Syrian and Iraqi issues, and the common dangers that threaten our security." He added in comments to reporters that he hopes to boost cooperation between Iraq and Syria to defeat those threats. Al-Jaafari also met with his Syrian counterpart, Walid al-Moallem, during his visit.

The Islamic State group has seized about a third of both Syria and Iraq.

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Associated Press writers Bassem Mroue in Beirut and Albert Aji in Damascus, Syria contributed to this report.