Russian President Vladimir Putin says Russia has information that the United States is planning to launch new missile strikes on Syria, and that there were plans for the USA to fake chemical weapons attacks there.
The warning came as G7 foreign ministers gathered in Lucca, Italy to consider a response to the chemical attack in Idlib province which killed more than 80 people, including many children.
Barrel bombs are oil drums or cylinders packed with explosives and shrapnel.
"By proxy Russian Federation is responsible for every civilian death last week", Fallon, whose government voiced support for U.S. President Donald Trump's decision to target the Syrian air base, wrote in the Sunday Times newspaper.
May and Merkel "expressed support for the action of the United States and agreed with President Trump on the importance of holding Syrian President Bashar al-Assad accountable", the White House said in a statement.
"Nothing has changed in our posture", a senior administration official said.
Alfano says Russian Federation should put pressure on Assad to stop the use of chemical weapons, and should join an worldwide push for peace in Syria.
Russian president Vladimir Putin and Iranian leader Hassan Rouhani said American military intervention was a "violation of global law" during telephone talks backing the Syrian regime.
Tillerson plans to use his meetings with foreign ministers from the Group of 7 industrialized economies - normally a venue for wonky economic discussions - to try to persuade leading countries to support the US plan.
Italian media said the aim was "to avert a risky military escalation".
The chemical attack has sent a new chill through relations between the West and Moscow, which backs Assad diplomatically and militarily and denies Syrian forces used chemical weapons.
"I think reality is setting in about how hard a partner (Russian President) Vladimir Putin will be, and I think events in Syria have underlined that for the administration", he added.
He said the gas attack and subsequent U.S. bombing of a Syrian air base had presented "a very substantial opportunity" to find a political solution to the six-year civil war.
'Russia can be a part of that future and play an important role, ' Tillerson said.
The U.S. has said its Syria strategy centers on persuading President Vladimir Putin to stop supporting Assad.
I think it's also worth thinking about Russian Federation has really aligned itself with the Assad regime, the Iranians, and Hezbollah.
Putin spoke before US Secretary of State Rex Tillerson was due to arrive in Moscow for talks with Russia's foreign minister. The Obama administration called the action an "uncontested arrival", and said the action was done out of weakness.
U.S. officials said the strike against the Shayrat airbase hit aircraft, fuel storage, weapons dumps and other equipment, and was aimed at sending a message to the Syrian regime that the use of chemical weapons would not be tolerated.