A bomb exploded in Damascus on Wednesday near a hotel used by United Nations monitors and wounded three people, Syrian state television said on Wednesday.

The bomb, which was placed in a car park behind the hotel, blew up a fuel truck which sent clouds of black smoke into the sky above the capital.

Syria's deputy foreign minister, Faisal Mekdad, said none of the observers had been wounded in the blast, state television said. "This was a criminal act aimed at distorting Syria's image," it quoted him as saying.

The target was not immediately clear. The area is home to the Syrian army officers club and a building belonging to the ruling Baath Party and is also not far from the army command.

Video from the site of the explosion broadcast by El-Ikhbariya, a pro-government channel, showed firemen hosing down a steaming fuel truck whose tank was blasted open near the hotel. A row of white UN vehicles parked nearby was covered in ash and dust.

A witness said the explosion had gone off at around 8.30 A.M. and damaged a building opposite the Dama Rose Hotel, where the monitors were staying, but appeared not to have damaged the hotel itself.

Meanwhile on Wednesday, the Swiss government applied an existing set of trade sanctions against Syria to the national airline, two other business organizations and 25 more people.

Spokeswoman Antje Baertschi of the State Secretariat for Economic Affairs, known as SECO, said the action makes Switzerland's sanctions applied to Syria last year "consistent" with those of the 27-nation European Union.

Baertschi says the sanctions now extend to Syrian Arab Airlines and include all financial and airport ground support it would have been provided, effectively blocking its national airline from operating on Swiss soil.

In a statement SECO says two other companies affected are the Aleppo-based national cotton production regulator known as the Cotton Marketing Organization and Drex Technologies SA because of owner Rami Makhlouf's support for his cousin President Bashar Assad.

Also on Wednesday, Human Rights Watch said  that Syrian government fighter jets had more than once attacked a key hospital in the northern city of Aleppo.

"Fighter jet attacks on a Al Shifaa Hospital in (the rebel-held) al-Shaar neighborhood in Aleppo twice in three days indicate that this was no accident," said Ole Solvang, emergencies researcher at the rights watchdog.

On Tuesday, former Syrian Prime Minister Riyad Hijab said President Bashar Assad's government is falling apart and only controls 30 percent of the country, in his first public appearance since defecting to the opposition.

He told a news conference in Jordan that the government's spirits were low after struggling for 17 months to crush the revolt against Assad's rule.

"Oh devoted revolutionaries, your revolution has become a model of effort and sacrifice for the sake of freedom and dignity. I assure you, from my experience and former position, that the regime is collapsing, spiritually and financially, as it escalates militarily," he said.