Residents gather around a convoy of UN vehicles carrying a team of UN chemical weapons experts at one of the sites of an alleged poison gas attack in the southwestern Damascus suburb of Mouadamiya, August 26, 2013.[Photo/Agencies]

Snipers shot at a UN team set to inspect the site of a suspected deadly chemical weapons attack on Monday, further ratcheting up tensions as the West warned of possible military action against Damascus.

A defiant Syrian President Bashar al-Assad declared that any strike by the United States and its allies would be doomed to failure and key ally Moscow said it could have dangerous consequences for the entire region.

A UN spokesman said unidentified snipers shot at the UN experts looking into allegations of a chemical attack near Damascus last week that the Syrian opposition claimed killed hundreds of civilians.

The attack forced them to suspend their inspection but no injuries were reported, said spokesman Martin Nesirky.

"The first vehicle of the chemical weapons investigation team was deliberately shot at multiple times by unidentified snipers," he said.

Syria blamed rebel forces for the attack, state television said on Monday.

Syria TV, citing an Information Ministry source, said the international experts were shot at by "terrorists", a term it commonly uses to describe rebels trying to topple Assad.

"The Syrian government will hold the armed terrorist groups responsible for the safety of the members of the United Nations team," the source added, according to state television.

The attack came as the West appeared to be moving closer to launching a military response over last Wednesday's attack near Damascus, which shocked the world after grisly pictures emerged of dead civilians.

Britain said the West could act even without full UN Security Council backing.

Washington and its allies have pointed the finger of blame at Assad for the alleged attack, the latest atrocity in a conflict that has claimed the lives of more than 100,000 people since March 2011.

Assad, in an interview with a Russian newspaper published on Monday, angrily denied the accusations as an "insult to common sense" and said any military action was doomed to failure.

"The US faces failure just like in all the previous wars they waged," he said.

A senior Syrian security official told AFP the government was ready to face "all scenarios".

"Western threats of strikes against Syria are part of the psychological and political pressure against Syria, but in any case we are ready to face all scenarios," the official said.

Russian Foreign Minister Sergei Lavrov warned his US counterpart John Kerry of the "extremely dangerous consequences of a possible new military intervention for the whole Middle East and North Africa region".

Syrian authorities had approved the UN inspection of the site in Ghouta east of Damascus on Sunday, but US officials said it was too little, too late, arguing that persistent shelling there in recent days had "corrupted" the site.

Mortar shells also hit a mosque in the center of Damascus on Monday, the Syrian news agency SANA said, blaming "terrorists".

AFP-Reuters