Fresh clashes in the Syrian capital Damascus have been described as the heaviest to take place in the city since fighting began over 15 months ago. The Red Cross has designated the conflict effectively as a civil war.
The offensive by the army appeared to be aimed at driving rebels from the Free Syrian Army (FSA) out of Damascus, activists said.
One activist said the Syrian army had shut down the road to the airport and was trying to surround fighters in the southern neighborhood of Tadamon, among others.
"There are hundreds of fighters in Damascus right now, we'll see what happens," the activist told the Reuters news agency.
"If the regime is able to crush the fighters in Tadamon the clashes should stop, but if not they may spread further."
Meanwhile, the Britain-based Syrian Observatory for Human Rights told the AFP news agency that the fighting in and around the capital had reached its most frenzied since the start of the uprising against President Bashar al-Assad's leadership.
"The regular army fired mortar rounds into several suburbs where rebels of the Free Syrian Army are entrenched," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights. "They have never been this intense," Rahman said.
New designation for conflict
As fighting intensified in the capital, the International Committee of the Red Cross (ICRC) said it now viewed the fighting as an internal armed conflict - effectively a civil war.
The qualification means those who order or commit attacks against civilians, such as murder, torture and rape, or use disproportionate force against civilian areas, can be charged with war crimes.
Previously, the ICRC has classed the violence as localized civil war in in three principal flashpoints - Homs, Hama and Idlib.
"We are now talking about a non-international armed conflict in the country," ICRC spokesman Hicham Hassan said. "That does not mean that all areas throughout the country are affected by hostilities," he added.
On Sunday, the government in Damascus contradicted the UN, which said it had used heavy weapons in an attack on the village of Tremseh. It said that 37 "terrorists" and two civilians had been killed in an attack using only light weapons. Opposition groups put the toll at around 200.
The Syrian Observatory for Human Rights claims that more than 17,000 people have been killed in the fighting since mid-march last year. The UN stopped compiling such figures at the end of 2011 and the numbers are not possible to verify independently.
On Monday, UN-Arab League envoy Kofi Annan and UN Secretary General Ban Ki-moon were on their way to Russia and China respectively to press the UN Security Council members to approve of action against the al-Assad administration.
rc/av (AFP, AP, Reuters)