Members of the al-Qaeda-linked group Nusra Front and other Syrian rebel factions have launched attacks on multiple army checkpoints and the governor's office in the Syrian city of Idlib.
The ensuing clashes have left at least 35 soldiers and rebels dead.
Monday's attacks revealed efforts by opposition fighters to extend their reach to the local capital of Idlib province, which is still under government control, since they seized scores of villages and towns in the northern province more than two years ago.
Mustafa al-Gharib, an activist in Idlib city, told Al Jazeera that rebels managed to temporarily take over the governorate building and kill a number of soldiers, before they withdrew.
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The UK-based Syrian Observatory for Human Rights said Nusra Front and other groups shelled the city 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.
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 Idlib city, near Mastoumeh Hill.
The Syrian 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.
The Nusra Front already has a strong presence in the province, and taking Idlib would be strategically important because it would allow them to cut vital government supply lines and give opposition groups control of a main city.
Rebels had seized control over the city in 2012 for a couple of days, but the government took it back.
Source: Al Jazeera and agencies