Gunmen have broken through the gates of a pro-government Syrian TV channel headquarters, bombing buildings and shooting dead three employees, state media said, in one of the boldest attacks yet on a symbol of the state.

President Bashar al-Assad declared late on Tuesday that his country was at war and Wednesday's attack on Ikhbariya's offices - located 20 km south of the capital - as well as overnight fighting on the outskirts of Damascus show that 16 months of violence is now rapidly encroaching on the capital.

Footage aired on Ikhbariya, which resumed broadcasting shortly after the attack, showed bullet holes pockmarked a two-storey concrete building and pools of blood on the floor. One building made of corrugated iron had been almost completely destroyed and flames licked at the metal frame.

Revolution forces and regime army units, meanwhile, have engaged in deadly combat around elite Republican Guard posts in the suburbs of Damascus on Tuesday, as 116 people were killed across the country, a monitoring group said.

Amid mounting tensions in the anti-government uprising now in its 16th month, Assad admitted that Syria is in a "real situation of war".

"When one is in a state of war, all our policies and capabilities must be used to secure victory," he told the new cabinet, the official SANA news agency reported.

The Syrian Observatory for Human Rights, a UK-based opposition group, said Tuesday's death toll comprised 68 civilians, 41 soldiers and seven revolution fighters.

"Violent clashes are taking place around positions of the Republican Guard in Qudsaya and Al-Hama," just kilometers away from central Damascus, Observatory head Rami Abdel Rahman told the AFP news agency in Beirut.

He said it was the first time that artillery was used "so close to the capital".

'Losing grip on power'

The United States said a "desperate" Assad was slowly losing his grip on power, citing defections and fighting raging increasingly close to Damascus, and offered new support to NATO ally Turkey after Syrian forces shot down one of its fighter planes last week.

"Clearly, Bashar al-Assad has been slowly - too slowly - losing his grip over his country," White House spokesman Jay Carney said on Air Force One as President Barack Obama flew to a campaign event in Atlanta.

"I would note that recent high-level military defections to Jordan and Turkey are another testament to the regime's loss of control over the situation in Syria."

"It is clear, however, that Assad is desperate to hang on to power at all cost, as evidenced by his continued use of air power and Shabiha gangs," Carney said, referring to the pro-government fighters in Syria.

Washington also pushed back on Russia's insistence that Iran should take part in a planned international conference on Syria in Geneva on Saturday.

"It is better to involve Iran in the settlement [of the Syrian crisis]," Russian President Vladimir Putin told a news conference in Jordan on Tuesday, adding that ignoring Iran would "complicate the process".

In Ankara, meanwhile, Turkish Prime Minister Recep Tayyip Erdogan said his country had changed its rules of engagement and would now treat any Syrian security threat as a military target after Friday's incident.

PHOTO CAPTION

Syria's President Bashar al-Assad speaks to the “new government” in Damascus in this handout photo distributed by Syrian News Agency (SANA) June 26, 2012.

Al-Jazeera