"So far according to our information, which correlates with Western data, the weapons are under control," he told journalists as he flew back to Moscow from an EU-Russia summit in Brussels, quoted by the Interfax news agency.
"The Syrian authorities have concentrated these stockpiles in one or two centres. Previously they were scattered around the country," he said.
President Bashar al-Assad's regime is doing all it can to ensure the weapons are secure, Lavrov said.
"Our American colleagues acknowledge that the main threat is if (the chemical weapons) are seized by the insurgents," he added. "For us this is very serious. We check every rumour that concerns chemical weapons."
The United States said earlier this month it had intelligence showing that the regime was considering using its chemical weapons.
US President Barack Obama led international warnings to Assad over the arsenal but Damascus insisted it would not use the weapons against its own people.
Russia remains one of the Syrian regime's last major allies after 21 months of deadly conflict and along with China has shielded Assad from UN sanctions over the brutal crackdown on dissent that has escalated into civil war.
Lavrov reiterated Russia's opposition to intervention in Syria, citing UN Security Council resolutions that NATO used to justify military strikes in Libya.
"We are convinced that the UN Security Council must not take any more ambiguous decisions, after our partners behaved so abominably over the resolution on Libya," he said.
In stinging criticisms of Western powers, Lavrov said he believed they lacked desire to intervene in the Syrian conflict and that their influence over the opposition to Assad's regime was waning.
"I have a feeling that no one has any appetite for external intervention," Lavrov told journalists
"I even have the feeling that they are praying for Russia and China to continue blocking permission for external intervention. Because if there is such a decision, they will have to act, and no one is ready to act," he said.
He said he believed the West was failing to influence Syria's newly formed opposition National Coalition, which Western and Arab states have endorsed as the sole representatives of the Syrian people.
"I think that the Western sponsors of this coalition are already losing their influence on it," he said.
Moscow still insists on the fulfilment of an agreement between world powers in Geneva earlier this year to solve the crisis through talks involving all parties.
At a news conference at the end of the EU-Russia summit, President Vladimir Putin called Friday for talks between all parties to prevent "chaos" in Syria although he denied propping up Assad's regime.
Moscow's position has frustrated Western attempts to end the bloodshed by forcing Assad from power. The West has also condemned Moscow's continued military ties with Damascus, its Soviet-era ally.