Syria's main opposition group is declining invitations to international meetings to protest what it calls the "shameful" failure by world leaders to end violence there.
"The international silence on the crimes committed every day against our people amounts to participating in two years of killings," the Syrian National Coalition said in a statement released Friday and reported on by Agence France-Presse and other news organizations.
"We hold the Russian leaders in particular ethically and politically responsible because they continue to support the [Damascus] regime with weapons," the statement said.
The group's leaders had received invitations to attend meetings in Moscow and Washington, D.C. Now, those meetings won't happen.
The coalition is also pulling out of a conference in Rome next month with the international coalition, Friends of Syria, which supports the opposition.
"The main significance of this decision to boycott international diplomatic meetings on Syria is that it effectively torpedoes the initiative launched by the coalition's own leader Moaz al-Khatib," the BBC's Jim Muir reported Saturday.
On Friday, three missile strikes fired by Syrian President Bashar Assad's forces killed more than 29 people in a rebel-held area of eastern Aleppo, according to the Syrian Observatory for Human Rights.
The Associated Press reports that fighting between rebels and regime troops intensified in Aleppo on Saturday as they struggle for control over the nation's second-largest airport.
Rebel forces control land outside of Aleppo and have been trying to take control of the city's airport for months.