The Syrian workers were destroying or disabling a "range of items", including "missile warheads, aerial bombs and mixing and filling equipment", the statement added.
The team faces the daunting task of disposing of an estimated 1,000 tonnes of the nerve agent sarin, mustard gas and other banned arms at dozens of sites in Syria by mid-2014.
The experts, who arrived on Tuesday, were also "monitoring, verifying and reporting" whether Assad's government provided accurate information on its chemical stockpiles.
As the operation got under way, President Bashar al-Assad admitted in an interview that his government had made "mistakes" in the country's brutal conflict.
But he again denied that his forces used chemical weapons in an August 21 attack that killed hundreds of civilians.
The assault led to threats of a US strike and eventually the UN resolution requiring Syria to turn over its arsenal.
In Damascus, meanwhile, a barrage of mortar rounds slammed into a Christian neighbourhood, killing eight people.
And UN-Arab League envoy Lakhdar Brahimi called on Assad's regime and the rebels to hold peace talks "without preconditions."
The OPCW has said other methods to render Syria's production facilities unusable could include explosives, sledgehammers or pouring concrete.
Syria agreed to give up its chemical arsenal under last month's UN resolution that enshrined an agreement struck between Washington and Moscow aimed at averting US military action.
Under the plan, Syria's chemical weapons mixing and production facilities must be destroyed by November 1.
UN leader Ban Ki-moon is expected to send a report to the Security Council on Monday setting out in more detail the logistics of what is considered one of the biggest and most dangerous disarmament operations ever staged because the Syria war is still raging.
Assad says 'mistakes happen'
Assad insisted his government was being "very transparent" with the UN-OPCW team.
"The experts can go to every site. They are going to get all the data from us, they will verify them, and then they can make a judgement about our credibility," he told Germany's Spiegel magazine.
The uprising that began in March 2011 initially took the form of peaceful protests against the Assad family's 40-year reign but escalated into a civil war after government forces fired on demonstrators.
More than 115,000 people have since been killed, activists say. Two million people have become refugees and millions more have been displaced inside Syria.
"Whenever political decisions are made, mistakes happen," Assad said.
"We all make mistakes. Even a president makes mistakes."
Although acknowledging that "reality is not black and white", he insisted that "our fundamental decisions were right".
"You can't just absolutely say 'they carry 100 percent of the blame and we carry zero'," Assad said.
"But basically it's correct that we are defending ourselves."
The president also lashed out at US accusations that he had killed his own people with chemical weapons, saying President Barack Obama "presents not a single piece of evidence. Not a shred of evidence.
"He has nothing to offer but lies," he added.
The magazine reported that German intelligence services believe Iran has allowed Assad's regime to station warplanes on its territory to protect them from foreign attack.
State news agency SANA said eight people were killed and 27 wounded in the Damascus district of Qassaa when four mortar rounds slammed into the Christian neighbourhood.
Rebels regularly fire into Damascus from rear bases in neighbourhoods around the city.
Despite the fighting, UN-Arab League peace envoy Brahimi told France's TV5 Monde that he hoped the two sides would agree to attend a peace conference in Geneva in mid-November "without preconditions".
"We are going to Geneva without preconditions," Brahimi said.
"Mr Bashar al-Assad cannot say that he does not want to negotiate with 'X' or 'Y' and it's the same thing for the opposition."