Two suicide bombers have struck the heart of the Syrian capital Damascus, killing at least 14 people and wounding at least 31 others, according to the pro-government television channel Al-Ikhbariya.
Activists said one of Tuesday's explosions took place inside a police station and that many among the dead were policemen.
A security official quoted by Al-Ikhbariya said the suicide bombers struck near a police station in the Marjeh Square in the heart of Damascus.
"Two suicide bombers attacked Marjeh Square causing casualties and material damage," the broadcaster said on Tuesday morning.
The channel screened images showing badly damaged vehicles and bloodied pavements.
"It seems the terrorists have struck again," said a television presenter, using the government’s term to refer to rebels fighting President Bashar al-Assad's troops.
The Britain-based Syrian Observatory for Human Rights (SOHR), which has a network of activists on the ground in Syria, said 15 were killed in the explosions, one of which was caused by a man who blew himself up inside the police station in the square.
The SOHR said the other explosion occurred outside the police station
Suicide and car bombs have become common in Damascus. Some of the deadliest attacks targeting security installations have been claimed by the al-Qaeda-linked Jabhat al-Nusra - one of scores of rebel factions fighting Assad's forces.
Separately, in Aleppo province the army launched multiple attacks on rebel positions, including rebel-held areas of the key Minnigh military airbase, the SOHR said.
"Parts of Minnigh military airbase were shelled by regime forces... Rebels are in control of large swathes of the airbase," the SOHR said on Tuesday.
A military source told AFP news agency heavy clashes were raging at the base for a third day, but denied any part of the airport was under rebel control.
He said the fighting was not part of a broader campaign that the regime has pledged to launch to re-take Aleppo city, large parts of which are in rebel hands, and other parts of the province.
But other areas of Aleppo were under fire, two days after pro-regime media said an army campaign in the province would began within "hours or days".
Regime forces shelled the opposition-controlled villages of Deir Hafer and Al-Bab, and hit the rebel stronghold of Marea with rockets, the Observatory said.
There were unconfirmed reports of a ground-to-ground missile strike in Aleppo province, the SOHR added.
Tuesday's developments came after Gulf Arab states promised sanctions against members of Hezbollah, the mainly Shia Lebanese political and military group, in retaliation for its intervention in Syria's ongoing civil war in support of Assad.
In-depth coverage of escalating violence across Syria
The six Sunni-led members of the Gulf Cooperation Council (GCC) issued a condemnation on Monday, according to a statement from the GCC secretariat carried by the Saudi Press Agency.
"The GCC ministerial council has decided to take measures against those enlisted in the party [Hezbollah] residing in the member states, whether with regard to their residencies or their financial and commercial dealings," it added, without giving any specific details.
Saudi Arabia and Qatar, both GCC members and US allies, have been explicit in calling for Assad to go, and have been arming the mostly Sunni rebels seeking to oust him and his mostly Alawite regime, members of an offshoot of Shia Islam.
The rebels suffered one of their biggest setbacks last week when Hezbollah fighters helped Assad's forces to retake the Syrian border town of Qusayr, which controls vital supply lines.
Hassan Nasrallah, Hezbollah's leader, said last week that Syria and Lebanon faced a common threat from radical Sunni Islamists.