NATO Secretary General Anders Fogh Rasmussen said on Wednesday that information from a wide variety of sources suggested the Syrian government had used chemical weapons in attacks near the Syrian capital, Damascus, last week.

"The Syrian regime maintains custody of stockpiles of chemical weapons. Information available from a wide variety of sources points to the Syrian regime as responsible for the use of chemical weapons in these attacks," he said in a statement after NATO ambassadors discussed the situation in Syria.

"This is a clear breach of long-standing international norms and practice. Any use of such weapons is unacceptable and cannot go unanswered. Those responsible must be held accountable," Rasmussen said, adding "We consider the use of chemical weapons as a threat to international peace and security."

The NATO chief stressed that the alliance would continue to consult on the issue and assist its member Turkey and protect its border with Syria.

The Syrian opposition claimed that 1,300 people were killed in a government chemical weapons attack on militant strongholds in the suburbs of Damascus last Wednesday. The Syrian government denied the allegation.

Rasmussen said that NATO allies expressed full support to the ongoing UN investigation, but deplored that the Syrian government failed to provide immediate and secure access for the UN inspectors to the sites of the attacks.