DAMASCUS, Syria — Members of the al-Qaida-linked Nusra Front and other Syrian rebel factions launched simultaneous attacks on army checkpoints and the governor's office in northwestern Syria on Monday, triggering hours-long clashes that left 19 troops and rebels dead.

The attacks all took place in the city of Idlib, activists and state media reported. The city, which is in Syrian government hands, is the local capital of Idlib province. Monday's attacks were the most serious there since Syrian rebels took control of scores of villages and towns around it more than two years ago.

The fighting is separate from the clashes underway between Nusra Front's main rebel rivals, the Islamic State group, and Syrian Kurdish fighters for control of the strategic border town of Kobani, further to the east and along the border with Turkey.

The Britain-based Syrian Observatory for Human Rights said Nusra Front and other groups shelled Idlib and simultaneously attacked army checkpoints there. It said four Nusra Front members blew themselves up inside the city, targeting checkpoints there and causing casualties among the troops.

"It was a moral blow to the regime," said activist Asad Kanjo, based in the town of Saraqeb, also in Idlib province. He added that calm had been restored in the city.

Syria's pro-government Al-Ikhbariya TV cited the provincial police chief, who was not named, as saying the attackers took advantage of a power cut before dawn after to hit the checkpoints and also the governor's office. He added that troops repelled the attackers.

"There isn't one gunman in the city now," said the police chief. The TV later aired footage from Idlib showing bodies of two purported attackers with suicide vests.

Another activist in Idlib province, speaking on condition of anonymity for fear of reprisals, said most of the attacks took place on the southern edge of the city, near Mastoumeh Hill.

The Observatory said the hill was captured by rebels, which prompted Syrian helicopter gunships to target the site. It said nine rebels and 10 soldiers were killed at the hill.

Syrian state TV said government forces repelled the attack on Idlib and that a "large number of terrorists" were killed. The government refers to the rebels as terrorists.

State TV said the attackers were led by Abu Waleed al-Libi who was killed in the battle — al-Libi is Arabic for "the Libyan." The Observatory said that some of the Nusra Front members killed in the fighting were foreigners.

Mroue reported from Beirut.