Fierce clashes in Syria killed at least 18 people Wednesday, mostly in Homs, as regime forces stormed and shelled villages in fresh operations, monitors said.

Seven people were killed in the central city of Homs -- four rebels who died in clashes with the regular army in the neighbourhood of Qussur and three civilians, including a man and his son, the Syrian Observatory of Human Rights said.

Also in Homs province, three civilians, including a woman were killed by rockets near the border with Lebanon, while a soldier was killed in heavy fighting in the rebel city of Qusayr.

In the province of Idlib in Jabal al-Zawiya area a former political prisoner Ahmed al-Othman and his brother were killed as tank fire struck their car.

An elderly man was also killed in indiscriminate firing in the province as houses were burned and raided in the village of Taftanaz, the Observatory said.

In Deir Ezzor, a rebel hiding in the village of Zibari was killed by gunfire, while in Damascus a "bomb under the car of a pro-regime man" exploded causing no casualties.

Three civilians were killed and 15 wounded in an explosion in a building in the town of Beit Sahem.

And in the province of Daraa, the cradle of uprising against the regime of President Bashar al-Assad, government forces stormed the village of Tafas and an arrest campaign was underway in Inkhel.

The bloodshed in Syria continues unabated despite the regime's pledge to enforce a peace plan proposed by UN-Arab League envoy Kofi Annan, and at least 80 civilians were killed on Tuesday.

On Wednesday, Syrian forces launched fresh military operations, storming and shelling several towns or villages, the Observatory said.

"From the Turkish border in the northeast to Daraa in the south, military operations are ongoing," Rami Abdel Rahman, head of the Britain-based group, told AFP.

"Tanks are still shelling or storming towns and villages before going back to their bases," he added. "That does not mean they are withdrawing."

The assaults were taking place despite Assad's pledge to implement by April 10 a peace plan brokered by Annan.

Abdel Rahman said regime forces early Wednesday stormed the village of al-Mazareb, located near the Jordanian border in Daraa province.

Clashes had also erupted in the town of Khirbet Ghazale, in Daraa province.

Activists said the army overnight stormed the town of Latame, in central Hama, and Saraqeb in Idlib province.

They said demonstrators in the city of Hama carried banners on Tuesday that read: "Despite all your shelling, nothing has died in us except fear."

Annan on Monday told the UN Security Council that Assad had agreed to "immediately" start pulling troops out of protest cities and complete a troop and heavy weapon withdrawal by April 10.

The revolt that broke out in Syria in March of last year has left more than 9,000 people dead, according to the United Nations.