BEIRUT (AP) -- Three bombs collapsed walls in the Syrian Interior Ministry building Wednesday in Damascus, killing at least five people, as rebels fighting to overthrow President Bashar Assad edged closer to the capital, the symbol of his power.
The blast came as more than 100 countries recognized the opposition umbrella group as the legitimate representative of Syria, a diplomatic blow to Assad.
Five people were killed in the Wednesday's attacks and 23 others were injured in the attacks, according to a statement by the Interior Ministry.
Such bombings have been a trademark of Islamic radicals fighting alongside the rebels, raising concerns about the extremists' role in the civil war.
On Wednesday afternoon, attackers detonated two explosive devices before an explosives-laden car went off near the entrance of the Interior Ministry building in Kafar Souseh district in Damascus. The blast knocked down walls inside the ministry building, scattering debris on the street and shattering windows in nearby structures, including at the Egyptian Embassy.
Police cordoned off the area. The pro-government Al-Ekhbariya TV showed splotches of blood on the street in front of the ministry.
Syrian TV said the Interior Minister Mohammed al-Shaar and senior officials at the ministry were unharmed.
There was no immediate claim of responsibility for the blasts. An al-Qaida linked group, Jabhat al-Nusra, has claimed many deadly bombings inside Syria in the past.
Rebels have targeted the center of Damascus with bomb attacks in the past, most dramatically in July when they detonated explosives inside a high-level crisis meeting in Damascus that killed four top regime officials, including Assad's brother-in-law and the defense minister.
Opposition fighters have been making inroads in their advance toward Damascus, capturing military bases as fighting intensified in the southern districts of the Syrian capital and its suburbs.
The conflict started nearly 21 months ago as an uprising against Assad, whose family has ruled the country for four decades. It quickly transformed into a civil war.
According to activists, more than 40,000 people have been killed since March 2011.
On the political front, more than 100 countries recognized a new opposition coalition as the legitimate representative of the Syrian people during an international meeting being held in Morocco. The U.S. also has declared the coalition is the "legitimate representative" of its country's people. The moves open the way for greater humanitarian assistance to the forces battling Assad and possibly even military aid.
The presence of extremist groups among the rebel forces has raised concerns in the U.S. and other nations that are supporting the opposition in Syria. They do not want to see extremists gain power in the region. The U.S. has blacklisted Jabhat al-Nusra -- Arabic for Victory Front -- as a foreign terrorist organization and said the group was part of al-Qaida in Iraq.
Al-Nusra fighters appear to be among the most effective fighting forces on the rebel side, spearheading many recent gains.
Western officials have raised concerns that an increasingly desperate Assad might unleash his chemical weapons stockpiles against rebels.
A U.S. official said Syria fired several Scud missiles at rebel positions in recent days. The missiles can carry chemical weapons, but the official said there was no evidence they were used. He spoke on condition of anonymity because he wasn't authorized to discuss the matter publicly.
Syria is believed to have a formidable arsenal of chemical weapons, including sarin and mustard gas, although its exact dimensions are not known. Syria is not a signatory to the 1997 Convention on Chemical Weapons and thus is not obliged to permit international inspection.
The government in Damascus has been careful not to confirm it has chemical weapons, while insisting it would never use such weapons against its own people.
On Wednesday, Human Rights Watch accused the Syrian military of using air-delivered incendiary bombs in at least four locations across Syria since mid-November.
At least 91 people were killed in fighting nationwide on Wednesday, according to the Britain-based Syrian Observatory for Human Rights that relies on reports from activists on the ground. Most heavy fighting was concentrated on the northern city of Aleppo, Damascus suburbs and northern province of Deir el-Zour.
An international aid group said tens of thousands of Syrians, many of them wounded, are trapped in Deir el-Zour, due to intense fighting and bombing.
In a statement Wednesday, Doctors Without Borders said local residents reported the city of Deir el-Zour is being "shelled and bombed daily." There is only one makeshift hospital with four doctors in Deir el-Zour, and those doctors are "completely exhausted after six months of working in a combat zone," said Patrick Wieland, a coordinator for the group. He said it is "virtually impossible to obtain medical supplies" in the besieged city.
In northern Syria, rebels clashed with pro-government Kurdish gunmen near the city of Ras al-Ayn along the border with Turkey, according to an official in the mayor's office in the Turkish border town of Ceylanpinar. At least 17 wounded Syrians were brought over to Turkey for treatment, and several died, the official said.
The official spoke on condition of anonymity because Turkish government rules bar civil servants from speaking to journalists without prior authorization.
Aji reported from Damascus. Associated Press writers Elizabeth A. Kennedy in Beirut, Robert Burns in Kabul, Afghanistan and Suzan Fraser in Ankara, Turkey contributed to this report.