Syrian President Bashar al-Assad has said his country is in "a state of war", more than a year after the uprising against his rule began.
Addressing his new cabinet, Mr Assad said that all efforts had to be directed towards winning the war.
Earlier, activists said fierce fighting in the suburbs of the capital Damascus had been the worst there so far.
The fresh clashes came amid heightened tensions with neighbouring Turkey over the downing of a military jet.
"We live in a real state of war from all angles," President Assad told members of the cabinet who were sworn in on Tuesday.
"When we are in a war, all policies and all sides and all sectors need to be directed at winning this war."
He criticised countries that have been calling for him to stand down, saying that the West "takes and never gives and this has been proven at every stage".
He added: "We want good relations with all countries but we must know where our interests lie."
Earlier the UK-based Syrian Observatory for Human Rights said that fierce clashes took place near Republican Guard positions in Qadsaya and al-Hama, about 8km (5 miles) from the centre of Damascus.
Correspondents say it is rare for fighting to take place near Republican Guard bases and suggests a growing confidence among the rebels.
The elite Republican Guard, led by President Assad's younger brother Maher, is tasked with protecting the capital.
State TV confirmed the fighting but said dozens of "terrorists" had been killed and many others taken prisoner, including foreign fighters.
It said large numbers of armed rebels had moved into al-Hama and tried to take control of a main road to the west in order to bring in more arms and fighters.
The Observatory said that 10 people had been killed by shelling in Qadsaya and some 58 people had died in violence across Syria on Tuesday - 24 soldiers, 30 civilians and four rebels. The figures cannot be independently verified.
Observatory head Rami Abdel Rahman told AFP news agency: "This is the first time that the regime has used artillery in fighting so close to the capital.
"This development is important because it's the heaviest fighting in the area and close to the heart of the capital."
Heavy shelling was also reported in Homs, where the International Committee of the Red Cross (ICRC) last week tried unsuccessfully to arrange the evacuation of civilians.
The ICRC said on Tuesday it was returning to the city for a fresh attempt.
On Tuesday, Turkey said the rules of engagement for its military had changed after Syria shot down a F-4 Phantom jet over the eastern Mediterranean last week.
Prime Minister Recep Tayyip Erdogan told parliament that if Syrian troops approached Turkey's borders, they would be seen as a threat.
"Every military element approaching Turkey from the Syrian border and representing a security risk and danger will be assessed as a military threat and will be treated as a military target," he said.
Syria insists that the F-4 Phantom was shot down because it was inside Syrian airspace. Turkey says the plane in international airspace.
Nato, of which Turkey is a member, convened an emergency meeting of its ambassadors on Monday and afterwards expressed "strong solidarity" with Ankara.
Relations between Syria and Turkey were already highly strained before the F-4 was shot down.
In other developments on Tuesday, the head of the UN's peacekeeping operations, Herve Ladsous, said its monitoring mission in Syria would remain suspended because of mounting violence.
Russia said its foreign minister Sergei Lavrov would attend an international conference on Syria which special envoy Kofi Annan hopes to hold in Geneva on 30 June.
However, Moscow is insisting that Iran also be allowed to attend, a move strongly opposed by the US and its allies.
Last year, in the wake of the Arab Spring uprisings, thousands of pro-democracy protesters took to the streets of Syria's cities demanding greater freedom and political reform.
The government's response was a brutal crackdown that left hundreds dead and inspired many opposition supporters to take up arms.
In April, following months of bloodshed, the Syrian government agreed to a six-point peace plan brokered by UN-Arab League envoy Kofi Annan.
UN monitors were deployed to Syria to oversee a ceasefire, but the truce never took hold.
The main rebel fighting group, the Free Syrian Army (FSA), has become increasingly better organised - and armed - and is in effective control of swathes of Idlib province and parts of Aleppo province in the north.