Another mortar shell from Syria has struck Turkish territory, prompting a fourth straight day of retaliatory artillery fire from the Turkish side.

The mortar landed in a rural area near the village of Guvecci early on Saturday morning, just minutes after intense fighting broke out between the forces of Syrian president Bashar al-Assad and the rebels in the village of Harabjoz, in Syria's Idlib province, the private Dogan news agency reported.

No one was hurt by the mortar, which landed some 500 metres outside of the village. But Turkish artillery based at an army battalion near Guvecci immediately responded with "counter-fire," the state-run Anadolu Agency said.

Villagers rushed out of homes and gathered at a safer point in the village, away from the border area.

The latest shelling comes a day after Turkish prime minister Recep Tayyip Erdogan called on Syria not to test Turkey's "limits and determination" and insisted that his country "was not bluffing" with its warnings.

Al-Assad's rare public appearance

Also on Saturday, al-Assad made a rare public appearance when he laid a wreath at the country's Unknown Soldier statue in Damascus to mark the 1973 war with Israel, also known in Syria as the October War. Syrian state television broadcast the ceremony.

Spotlight In-depth coverage of escalating violence across Syria

The Syrian likened the current crisis to the war with Israel. Damascus denies it is facing a popular uprising, instead blaming the violence on a foreign conspiracy linked to its support for anti-Israeli groups such as Lebanon's Hezbollah.

"There are few differences between the current aggression and the circumstances during the October War, as Syria is facing an enemy armed with Western and Israeli weapons aiming at destroying the Syrian state and punishing its people for foiling all the hegemonic and hostile schemes planned for the region," the official news agency SANA commented.

Lebanese security officials meanwhile said Syrian troops backed by warplanes and helicopters gunships began a major attack against rebel-held areas near the Syrian town of Quseir adjoining Lebanon's Bekaa Valley. The Lebanese-Syrian border has also been the site of deadly border incidents.

The officials, who spoke on condition of anonymity in line with regulations, said no shells fell on the Lebanese side of the border on Saturday. They added that Lebanese troops were put on high alert in the border area to make sure the fighting does not reach Lebanon.

The Observatory and the Local Coordination Committees, another activist group, reported intense shelling at rebel-held areas in the northern city of Aleppo and the central city of Homs. They said the government shelling of the town of Taibeh near Homs killed at least 10 people and wounded dozens.