Syrian rebels and government forces on Tuesday were fighting for the control of a key government-held area near the Turkish border, a rebel commander told dpa.
"The rebels are fighting to control the area of Wadi al-Daif in the region of Maaret al-Nouman, where regime forces have positioned most of the artillery batteries that are shelling areas in the Idlib province," said Abu Saeed, a Free Syrian Army commander.
"Fighting on the ground is fierce and warplanes are helping the troops by bombarding areas in Maaret al-Nouman."
The clashes came a day after a Syrian shell landed in the Turkish province of Hatay, prompting Turkey to fire retaliatory shells into Syria.
The opposition Syrian Observatory for Human rights said Monday's death toll across Syria reached 210 people and stood at 4,727 in September.
Some 32,000 people - most of them civilians - have been killed since the uprising against President Bashar al-Assad began in March 2011, it said.
Overnight Monday, bomb blasts hit a security compound on the edge of Damascus overnight, in the latest attack by rebels against units loyal to President Bashar Assad, activists said.
Al-Nusra, a militant Islamist group, said in a statement on Facebook it carried out the attack on the Air Force Intelligence complex in the suburb of Harasta using two suicide car bombs loaded with tones of explosives.
Video footage taken by activists, which could not be independently verified, showed a large explosion. Syrian state television said an explosion occurred in the area but gave no details.