A senior UN disarmament official has arrived in Damascus to push for allowing UN inspectors access to the site of a suspected chemical weapons attack.
Angela Kane, the UN High Representative for Disarmament Affairs, did not comment to reporters on Saturday as she entered the Four Seasons hotel, which is located only a few miles from the site of Wednesday's reported chemical weapons attack in the outskirts of the Syrian capital.
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UN inspectors arrived in Damascus on a mission to investigate claims of the use of chemical weapons just days before the attack that, according to rebels and activists, killed hundreds of civilians.
The developments came as Hassan Rouhani, the Iranian president, acknowledged for the first time that chemical weapons had killed people in Syria and called on the international community to prevent their use.
He stopped short of saying who he believed had used them.
Iran, a close ally of the Syrian regime of Bashar al-Assad, has previously accused the rebels in the country of being behind what it called suspected chemical attacks.
"Many of the innocent people of Syria have been injured and martyred by chemical agents and this is unfortunate," Rouhani was quoted as saying by Iran's ISNA news agency.
"We completely and strongly condemn the use of chemical weapons."
Mehr, another Iranian news agency, quoted Rouhani as saying: "The Islamic Republic gives notice to the international community to use all its might to prevent the use of these weapons anywhere in the world, especially in Syria."
|Mark Kimmitt, former deputy director of plans and strategy at US Central Command, talks to Al Jazeera on the claims of use of chemical weapons in Syria
Footage shot by an independent journalist for Britain's ITV News appears to show the victims of the incident.
Also on Saturday, the president of the opposition Syrian National Coalition (SNC) called on world leaders to act firmly against Damascus.
Ahmad al-Jarba said that the Syrian government was responsible for "crime of genocide" and it was time for world leaders to be serious and firm and interfere "by all means" against the Syrian president.
Against this backdrop of escalating Syria-related tensions, the US navy is reported to be expanding its presence in the Mediterranean Sea with a fourth cruise-missile warship.
Earlier, Chuck Hagel, the US defence secretary, indicated that the US was positioning assets in anticipation of any decision by President Barack Obama to order military action on Syria.
Obama's security advisers are expected to convene at the White House this weekend to discuss US options regarding Syria.