Breaking news - Syrian capital 'rocked by blasts' From The BBC

A series of explosions and gunfire rocked the Syrian capital Damascus on Tuesday evening, reports say.
Sources said between three and five explosions were heard in the west of the city from about 1600 GMT. The blasts were followed by heavy gunfire.

More in the article.

Funny, I just posted about something like this earlier today.

UPDATE: From The New York Times

DAMASCUS, Syria (AP) -- Syrian security forces clashed with a "terrorist band" late Tuesday in Damascus, Syrian television reported. Explosions and gunfire were heard in a neighborhood where foreign diplomats live and work.

There was no immediate word on casualties.

Syrian television, in a brief statement, said the "terrorist band" opened fire indiscriminately. Security forces gave chase and were in control of the situation. It gave no other details.

Syria has not seen such violence in years.

Residents of the area had reported explosions and gunfire in the Mazza neighborhood. Security forces sealed off the area, said the residents

[...]

Al-Jazeera reported that car bombs were used in the attack and that heavy exchanges of gunfire were continuing late into the night.

Al-Arabiya quoted a witness saying more than 15 explosions were heard.

UPDATE II: Background information from Bradenton.com

During the late 1970s and early 1980s, Syria's hard-line government fought a fierce war with Islamic fundamentalists of the Muslim Brotherhood, which was blamed for a 1980 assassination attempt on President Hafez Assad, the country's authoritarian leader. Assad was succeeded by his son, Bashar Assad, after his death of natural causes in 2000.

Assad suffered minor injuries after gunmen open fire with automatic weapons and grenades in the 1980 attack.

Syrian special forces troops massacred some 1,000 Muslim Brotherhood members in Tadmur Military Prison near Palmyra to avenge the assassination attempt.

In 1982, the Muslim Brotherhood staged a rebellion in the northern province of Hama. During the clashes, Syrian forces razed much of the city, killing as many as 10,000 people and finally crushing the Brotherhood after five-year war.

UPDATE III: From Yahoo News

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.

"There was no damage to the British Embassy."

Israeli television reported five blasts, one outside the British ambassador's residence, and said the Saudi embassy was also among the targets.

Too early to tell on all this.