A rebel shelling barrage targeting Damascus, Syria, early Thursday left at least five people dead and scores wounded, according to government and opposition accounts.
The attack was the second major rocket and mortar strike in recent weeks on the Syrian capital, which is under tight military control. Central Damascus neighborhoods have largely been spared the massive destruction and fighting evident in many outlying districts.
Video from Damascus shows plumes of smoke rising from various neighborhoods, including the historic Old City and several upscale residential districts. Residents reported repeated thuds from the shelling.
The attacks came as a rebel commander based outside the capital vowed to rain destruction on Damascus in retaliation for government bombardment of opposition-held areas.
The state news agency reported at least five civilians killed Thursday and more than 50 wounded, some in critical condition, along with damage to cars and buildings.
State media laid the blame for the attack on "terrorists," the government's term for rebels fighting to overthrow President Bashar Assad.
The bombardment of the capital consisted of more than 100 rockets, according to the Syrian Observatory for Human Rights, a pro-opposition group based in Britain.
Separately, the observatory said at least 12 people had been killed in government aerial bombardment of rebel-held areas outside Damascus.
Rockets and mortar shells fired from rebel-controlled areas have periodically hit Damascus, causing large numbers of civilian casualties. But Thursday's barrage and an attack on Jan. 25 that reportedly killed seven were especially intense, shattering the capital's tenuous calm.
The observatory said Thursday's assault was carried out by the Islam Army, an extremist faction based in the Ghouta region east of Damascus. The Syrian military has been unable to win back the Ghouta area, which has been largely under rebel control for years.
The Islam Army, regarded as the most powerful rebel group in the Damascus area, is part of the Islamic Front alliance, with links to Al Qaeda.
The Islam Army's leader, Zahran Alloush, has strong ties to Saudi Arabia, which has aided Syrian rebels and called on Assad to step down. Alloush was released from a Syrian prison in mid-2011 as part of an amnesty.
In postings on Twitter, Alloush said the attacks on the capital were in retaliation for "awful massacres" arising from government airstrikes on the Ghouta area, which includes the city of Duma.
This week, Alloush issued a statement on Twitter declaring all of Damascus "a military zone and an operations theater," and asking civilians to stay away from government buildings and military checkpoints.
The capital is replete with checkpoints and government structures, however, and rebel shelling routinely hits civilian targets.
The almost four-year Syrian conflict has resulted in tens of thousands of deaths, left towns and neighborhoods destroyed and forced millions to flee their homes. All diplomatic efforts to end the war have failed. Large swaths of Syria remain under the control of radical Islamist groups.
Times staff writer McDonnell reported from Beirut and special correspondent Bulos from Amman, Jordan.