BEIRUT— Syrian troops attacked a rebel-held town in the center of the country with helicopter gunships on Monday and shelled other restive areas, activists said.
The aerial assault targeted the strategic river crossing town of Rastan that has resisted repeated government offensives for months, they said.
It is part of an escalation of violence in recent weeks that comes despite an internationally brokered cease-fire that was supposed to go into effect on 12 April but never took hold.
"The regime is now using helicopters more after its ground troops suffered major losses," said Rami Abdel Rahman of the Syrian Observatory for Human Rights. "Dozens of vehicles have been destroyed or damaged" since the end of May.
Syrian Foreign Ministry spokesman Jihad Makdissi recently said that rebels are now using sophisticated anti-tank missiles. Videos posted by activists over the past week have shown many destroyed tanks and armored personnel carriers.
The Observatory and the Local Coordination Committees also reported government shelling in the central provinces of Homs and Hama, the southern region of Deraa, the northern province of Aleppo, and suburbs of the capital Damascus and Deir al-Zour in the east.
The Observatory reported the deaths of four civilians and an army defector in shelling in the area of Ashara in Deir al-Zour, and said another eight unidentified bodies had been discovered nearby. It reported three dead in the Hama shelling.
In Moscow, the Foreign Ministry said Foreign Minister Sergey Lavrov will visit Iran on Wednesday. Russia and Iran are Syrian President Bashar al-Assad's strongest allies. Moscow and China have vetoed two Security Council resolutions that threatened possible sanctions against Syria.
The ministry said in a statement that Russia is not playing the role of advocate for certain Middle East regimes.
"We are speaking for the strict observance of the norms and principles of international law in the interest of supporting regional stability and security in the Near and Middle East and North Africa," it said.
Syrian activists say the violence has claimed the lives of more than 13,000 people. On Sunday, activists said government shelling killed at least 38 people in the rebellious Homs district in the country's center. It was impossible to independently confirm the death toll.
British Foreign Secretary William Hague said Sunday that he could not rule out military intervention in Syria, saying the situation there is beginning to resemble the violence that gripped Bosnia in the 1990s.
Hague told Sky News television that time was "clearly running short" to implement international envoy Kofi Annan's cease-fire plan.
Hague said Syria was "on the edge of collapse or of a sectarian civil war, so I don't think we can rule anything out."
