Russia is claiming that the Syrian military is concentrating its chemcial weapons in one or two places in order to safeguard them from falling into the hands of terrorists.
Mr Lavrov told journalists on a flight returning to Moscow from an EU-Russia summit in Brussels: "According to the information we have, as well as the data of the US and European special services, the [Syrian] government is doing everything to secure [its chemical stockpiles].
"The Syrian government has concentrated the stockpiles in one or two centres, unlike the past when they were scattered across the country."
Mr Lavrov said the biggest threat from Syria's chemical weapons would be if militants managed to capture them.
The US fears Syria may be tempted to use the weapons if its situation becomes more desperate.
Mike Rogers, the chairman of the US House Committee on Intelligence, told the BBC a regional plan was needed to secure the weapons "immediately".
"If not, we're going to have a very major destabilising event in the region," Mr Rogers said.
US President Barack Obama warned President Assad this month he would face "consequences" if chemical weapons were turned on the Syrian people, saying it would be "totally unacceptable".
The US has said this would be a "red line" that might trigger military intervention.
Mr Lavrov said he believed Western powers had no appetite to intervene.
"I 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."
If Syria is concentrating its stockpiles, it will make a much simpler matter to seize and control them if it becomes necessary. And while Assad appears to be in no immediate danger of being overthrown, a quick strike by terrorists on some of those sites might have resulted in catastrophe. Now that they appear to be resasonably well guarded, they can be watched closely to make sure the terrorists don't get their hands on them.