"The OPCW mission has now conducted verification activities at a total of 11 sites that are identified by Syria's disclosure," the Hague-based Organisation for the Prohibition of Chemical Weapons said.
The OPCW has said that there are a total of 20 sites to be visited in Syria.
Since inspectors arrived in the country two weeks ago, activities have also included "critical equipment destruction at six sites as well as some Category 3 weapons destruction", the organisation added in a statement.
The OPCW and the United Nations now have about 60 experts working in Syria to eradicate chemical weapons, around a month after the OPCW accepted President Bashar al-Assad's application to join the Chemical Weapons Convention, in a bid to stave off a possible Western military strike.
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The key convention came into force on Monday.
So far Syria has won rare praise for its cooperation with the inspectors, but the UN has stressed that key deadlines in the destruction of the war-ravaged country's chemical weapons should be met.
Inspectors have until June 30, 2014 to complete the destruction of Syria's chemical arsenal.