At least 45 people were killed Tuesday across Syria, including 22 members of the security forces, as Syrians poured across the border to Lebanon and Turkey, activists said, dpa reported.
The violence coincided with a decree by President Bashar al-Assad announcing parliamentary elections for May 7, the state-run SANA news agency reported.
A referendum was held in February on a new constitution, and al-Assad vowed to hold parliamentary elections within 90 days. The opposition has dismissed the referendum "as a charade and a farce."
The new constitution allows for an end to the Baath party's five-decade monopoly on power. The new charter states that the president can serve only two seven-year terms and that a Supreme Constitutional Court will oversee free and fair elections.
In Washington, US State Department spokeswoman Victoria Nuland said: "Parliamentary elections for a rubber-stamp parliament in the middle of the kind of violence that we're seeing across the country is ridiculous."
Twelve soldiers were reportedly killed Tuesday in a rebel ambush on the van in which they were riding in the southern province of Daraa, the London-based Syrian Observatory for Human Rights said.
"The ambush took place as the squad was entering the city of Daal to arrest a number of activists in the area," the watchdog group said, adding that five rebels were wounded in the subsequent firefight.
In the north-western province of Idlib, at least 10 soldiers were killed in a rebel attack on an army checkpoint, the Observatory said.
On Monday night, security forces executed 44 men near al-Bilal mosque in Idlib, activists claimed.
In the province of Homs, 15 civilians were killed, including eight members of the same family, activists in northern Lebanon said.
The violence and news of "massacres" in the provinces of Idlib and Homs prompted many Syrian refugees to flee into Lebanon and Turkey.
Around 50 families, mainly from the Bab al-Sibaa neighbourhood in Homs, had arrived since Monday in Lebanon's northern city of Tripoli, while as many 300 people managed to flee areas in Idlib toward the Turkish border, activists said.
In Geneva, United Nations High Commissioner for Refugees Panos Moumtzis said that some 30,000 Syrians had fled to neighbouring countries since the unrest began a year ago.
Almost 23,000 people had been housed in Turkish refugee camps, but 10,000 had returned to Syria, Moumtzis said, noting that more than 12,000 Syrians had fled to Lebanon and 7,000 to Jordan.
Kofi Annan, UN-Arab League special envoy to Syria, held talks Tuesday in Ankara with Syrian opposition leader Burhan Ghalioun.
"The Syrian army is openly killing people. If they don't stop, we will have to take serious measures," Ghalioun told Turkey's state-run Anatolia news agency. "Syria is at a turning point."
Annan told reporters he was awaiting a response from Damascus on "concrete proposals," which he had submitted to al-Assad in talks over the weekend in Damascus.
"I am expecting to hear from Syrian authorities today (Tuesday) since I left some concrete proposals for them to consider," he said.
The New York-based Human Rights Watch said Syrian forces had laid landmines near the borders with Lebanon and Turkey to prevent civilians from fleeing.
A 28-year-old former Syrian army bomb disposal expert told the watchdog group that he and his colleagues removed around 300 mines in northern Syria in early March, and that local residents had seen government troops plant landmines along routes used by refugees to reach Turkey.
HRW called on Syria to cease its use of anti-personnel landmines and recognize that planting this internationally banned weapon will injure Syrians for years to come.
In Washington, Nuland condemned Syria's reported use of land mines: "Using something that was designed for purely military purposes, to fence their own people in - it's just horrific."