An explosion wounded six Syrian soldiers as they escorted a convoy of UN observers in the flashpoint town of Dera'a, according to reports.
The blast went off at the entrance to Dera'a, according to an AFP photographer in the southern town where an uprising erupted against the regime of President Bashar al-Assad in March last year.
The head of a UN observer mission to Syria, Major General Robert Mood, escaped unharmed when the blast went off as his convoy entered the restive town.
Separately, at least two Syrian troops and one civilian have been killed today as violence flared across the country and regime forces pounded a rebel hideout near Damascus.
Residents of Douma, about eight miles from the capital, reported heavy shelling since dawn and bursts of gunfire in the town, said the Syrian Observatory for Human Rights.
Rebels fighting to overthrow the regime of President Bashar al-Assad have apparently sought refuge in Douma.
In Damascus itself, clashes erupted briefly between a security patrol and rebels in the neighbourhood of Maisat, but there were no casualties, said the Britain-based Observatory.
In the eastern province of Deir Ezzor, security forces carried out raids and arrests in the villages of Al-Safira and Al-Hisan.
Two members of Syrian security forces were killed after midnight in the Jura district of Deir Ezzor, the scene of heavy shooting and explosions, the watchdog reported.
On Tuesday evening, a man was killed in the town of Soura in Deir Ezzor after unidentified gunmen attacked his car, leaving his daughter wounded.
One civilian was killed and three wounded in heavy machinegun fire by regime forces in Tell Ain al-Hamra, near the town of Jisr al-Shughur in the northwest province of Idlib, on Wednesday.
"Jisr al-Shughur is near the Turkish border and has had a significant presence of rebels since the beginning of the revolt," the Observatory's Rami Abdel Rahman said.
Rural villages east of Jisr al-Shughur and the town itself came under mortar attack by security forces, he added.
In the same province, in the village of Ahsem, an army checkpoint was targeted by an explosion followed by gunfire, the Observatory reported.
Shots were also heard early Wednesday in several districts of the central Syrian city of Homs, a stronghold of opposition groups.
UN envoy Kofi Annan on Tuesday said his peace plan that went into effect April 12 but has since been regularly violated by both sides to the conflict was "probably the last chance to avoid civil war" in Syria.
Nearly 12,000 people, mostly civilians, have been killed in Syria since an anti-regime uprising erupted in mid-March last year, according to the Observatory.