Syrian security forces killed three attackers and captured another in clashes this evening in an upmarket district of Damascus. A former United Nations building in the city was reportedly on fire following the attacks.
Syria said its security forces had confronted an armed group that opened fire in an upmarket Damascus area and brought the situation under control.
It was reported tonight that the assailants set off an explosive device at the former United Nations office in the Syrian capital, killing one of the militants, wounding another and setting the building ablaze.
"A subversive armed group opened fire at random this evening in the Mazze area and was confronted by the relevant security apparatus," the official SANA newsagency quoted a Syrian security official as saying.
"The situation is totally under control."
A United Nations spokeswoman in New York said a building formerly occupied by the UN in Damascus may have been targeted.
Marie Okabe, said the targeted building may have been the former offices of the UN Disengagement Observer Force, which oversees an agreement between Israeli and Syrian forces in the Golan Heights.
"It is our understanding that a building formerly occupied by UNDOF, which is still known as a UN building, may have been hit," she said.
"Our preliminary information is that all UN staff and facilities are safe and accounted for," she said.
The United Nations Development Fund and its Children's Fund also are in Mazza.
A series of loud explosions and heavy shooting broke out in the Syrian capital at around 4pm GMT in a western area of Damascus where foreign embassies are located, witnesses and media reports said.
"We were working in the library and heard lots of gunfire and explosions," said one foreign student in Damascus who was close to the site of the explosions.
"Everyone was terrified and we ran out of the building to see what was happening," he told reporters. "We saw some big puffs of smoke, but things are closed off now."
Ambulances and other emergency vehicles rushed to the scene and heavy security was in place throughout the city.
Two trucks laden with riot police were stationed near the ancient city's main square and by the state television building.
"The explosions were so strong that we felt as if there must have been a raid," a resident near the British embassy said.
A British Foreign Office spokeswoman in London said an explosion took place on a street close to the Iranian Ambassador's residence.
"It is closer to the Iranian ambassador's residence than it is to our ambassador's residence... (There were no) injuries to UK embassy staff but our staff are in the process of assessing the situation," she said.
Arab Al Arabiya television reported more than 15 blasts in an area housing diplomatic buildings belonging to Canada, Britain and Iran and a witness told the station the explosions were continuing.
But one Damascus resident, living some kilometres (miles) from the embassy area, said he heard only one loud blast.
"I was on my balcony when I heard this explosion. It was a single, deep boom that resonated somewhat. It came from the western part of the city. We think it was in a neighbourhood called Mezza," American resident Joseph Yackley told journalists.
Syria has seen little violence under the tight security imposed by the government of Bashar al-Assad who took over from his father in 2000, but there was fighting between security forces and restive Syrian Kurds last month.