A day before a team from the international chemical weapons watchdog watchdog was set to arrive in Douma, just east of Damascus, Sergei Lavrov said Russian experts have already inspected the site of the alleged attack and found no trace of chemical weapons.
He said Moscow has “irrefutable information that it was another fabrication.”
He offered no further evidence to back up his claim.
Mr Lavrov said “intelligence agencies of a state that is now striving to spearhead a Russo-phobic campaign were involved in that fabrication.”
He did not elaborate or name the state, but seemed to be hinting at the United States, Britain or France.
In a reference to the US, Mr Lavrov said “it would only benefit those who are protected by the ocean… and engage in continuous efforts to stir up the region in order to advance their geopolitical goals.”
Eastern Ghouta bombings: Syrian war in pictures
He also said even the smallest miscalculation in Syria could lead to new waves of migrants.
“God forbid anything adventurous will be done in Syria following the Libyan and Iraqi experience,” Mr Lavrov told a news conference.
He said ultimatums and threats do not help the dialogue.
A team of experts from the global chemical weapons watchdog, the Organisation for the Prohibition of Chemical Weapons (OPCW), was travelling to Syria and will start its investigations in Douma on Saturday.
On Wednesday, President Donald Trump warned missiles “will be coming” in response to the strike.
Theresa May won backing from her senior ministers to take action along with the United States and France to deter the Syrian regime from further use of chemical weapons.
Mr Trump himself appeared to cast doubt on at least the timing of any US-led military action, tweeting: “Never said when an attack on Syria would take place. Could be very soon or not so soon at all!”
He met his national security team on the situation in Syria on Thursday and “no final decision has been made,” the White House said in a statement.
“We are continuing to assess intelligence and are engaged in conversations with our partners and allies,” it said.