ALEPPO, Syria (Reuters) - A bomb exploded in central Damascus on Wednesday near several military buildings and a hotel housing U.N. observers, wounding three people and sending a pillar of black smoke into the sky above the Syrian capital.
No U.N. staff were hurt in the blast, which occurred exactly four weeks after a bomb killed four of President Bashar al-Assad's top security officials, including his brother-in-law.
Syrian Deputy Foreign Minister Faisal Mekdad told reporters at the scene that the bombing proved "the criminal and barbaric nature of those who carry out these attacks - and their backers in Syria and abroad".
Firefighters were dousing a fuel tanker set ablaze when the bomb detonated at 8.30 am (0530 GMT) in a car park behind the hotel. Ash and dust covered white U.N. vehicles parked nearby.
U.N. emergency relief coordinator Valerie Amos, on a mission to seek more access for aid deliveries, was meeting E.U. officials in Damascus when the bomb exploded.
Although the explosion occurred close to the hotel, its target was not clear. The area is home to a Syrian army officers' club and a building belonging to the ruling Baath Party. It is also not far from the army command.
Groups calling themselves The Descendants of the Prophet Brigade and the al-Habib al-Mustafa Brigade said on a Facebook page they were jointly responsible for the bombing, which they said had killed 50 soldiers. Competing rebel groups often claim attacks and it is usually unclear who was actually behind them.
Assad's troops launched a successful counter-offensive last month against insurgents who seized several districts of Damascus. They are still trying to dislodge rebels from swathes of Aleppo, Syria's biggest city and its economic capital.
More than 160 people, including 105 civilians, were killed across Syria on Tuesday, an opposition watchdog reported.
The violence in Syria, where opposition sources say 18,000 people have been killed since the uprising against Assad erupted in March last year, has divided regional and world powers.
Their disputes have nullified diplomatic peace efforts and effectively paralyzed the U.N. Security Council on Syria.
ISLAMIC OSTRACISM
Muslim heads of state were expected to suspend Syria from the Organisation of Islamic Cooperation at a summit in Mecca on Wednesday, over the objections of Iran, Assad's closest ally.
The decision by the 57-member body is symbolic and will have little practical effect on Syria, but it will underline Assad's isolation in much of the Sunni-majority Islamic world.
Syria's own Sunni majority is the dynamo of the revolt against Assad, whose Shi'ite-rooted Alawite minority is at the core of a ruling system based on the army and security services.
Syria has become another arena in a wider sectarian-tinged tussle pitting Shi'ite Iran against Saudi Arabia and its Sunni-ruled Gulf allies, who are backed by the West despite their own evident distaste for democracy. Turkey has also turned against Assad to become a focus of efforts to topple its former friend.
Nevertheless, to preserve a facade of Muslim unity, Saudi King Abdullah welcomed leaders to the Mecca summit with Iranian President Mahmoud Ahmadinejad beside him. The two men were shown on Saudi state TV talking and laughing together.
"It was a message to the Iranian nation and, I assume, to the Saudi people, that we are Muslim and we have to work together and forget about our differences," said Abdullah al-Shammari, a Saudi political analyst.
When it comes to Syria, those gaps appear insurmountable, with Saudi Arabia, Qatar and Turkey supporting the rebels, and Iran determined to prop up a proven ally who has provided vital logistical support for its Shi'ite ally Hezbollah in Lebanon.
Turkey's ties with Iran, an important trade partner and energy supplier, have also worsened over Syria and over U.S.-led efforts to punish Tehran for its disputed nuclear program.
Ankara and Washington have pledged to step up aid to the Syrian opposition and planning for a post-Assad Syria.
"NO COMMITMENTS"
Secretary of State Hillary Clinton said on Saturday the United States and Turkey were looking at all ways to help Syrian rebel forces, possibly including a no-fly zone.
U.S. officials have since emphasized that no such step toward direct military intervention was likely any time soon.
"Of course we should evaluate these issues. However, our discussions of these issues with Turkey should not suggest we are making commitments to set up these zones," U.S. ambassador to Ankara Frank Ricciardone was quoted as saying.
"There are serious legal and practical obstacles on this issue," he said of proposals for a no-fly zone or buffer zone in Syria, according to Turkish newspapers he had briefed.
"We will work on the subjects of a transition phase and buffer zone within the U.N. Security Council in line with international law," Ricciardone was reported as saying.
A NATO-led no-fly zone and bombing campaign helped Libyan rebels overthrow Muammar Gaddafi last year. But the United States and its European allies have been reluctant to take an overt military role in Syria's 17-month-old conflict.
In another sign of how the upheaval is spilling across Syria's borders, a prominent Shi'ite clan in Lebanon said it had abducted more than 20 Syrians there in retaliation for the kidnapping of one of their relatives by rebels in Damascus.
Clan member Maher al-Meqdad said the abductions were a response to the capture of Hassan al-Meqdad in Damascus two days ago by the rebel Free Syrian Army, which said he had been sent to Syria by Hezbollah.
Maher al-Meqdad said his relative had gone to Syria before the uprising began and had no links to the fighting there.
Syria's uprising has polarized Lebanon, where Sunnis mostly support the rebels, while Hezbollah backs Assad.
(Additional reporting by Tom Perry and Erika Solomon in Beirut, Asma Alsharif in Jeddah and Angus McDowall in Riyadh and Stephanie Nebehay in Geneva; Writing by Alistair Lyon; Editing by Jon Boyle)
