Russia was roundly criticized by Western diplomats and the Syrian opposition for waging lethal air strikes and backing the Syrian regime's on-the-ground advances, even during peace talks.
On the day the talks opened in Geneva on February 1, opposition delegates accused Russia and the Syrian regime of being as brutal as Nazi Germany in an escalating offensive and said they would not join the negotiations in earnest until that stops.
"The regime is the one killing the Syrian people," said Salem al-Mislet, spokesman for the largest opposition coalition, the High Negotiations Committee, when asked by a Russia reporter about the militant Army of Islam group that is in the opposition's delegation. "The regime in Russia will produce a new Hitler, and we are suffering from another Hitler in Syria."
The opposition coalition had delayed the start of the negotiations with a boycott aimed at forcing the Syrian regime to allow humanitarian aid to reach rebel-held cities under siege by the government.
The Syrian government on February 1 approved a United Nations request for new aid deliveries to three besieged towns where hundreds of civilians are facing starvation: Madaya, which is held by rebels, and Foua and Kfarya, which are held by the government.
The three villages are among 15 besieged communities across Syria, where the UN estimates more than 400,000 people are suffering.
While the government appeared to respond in part to demands that it ease the way for humanitarian aid, Syrian troops on the ground continued to advance closer to cutting off vital rebel supply lines to the northern city of Aleppo by capturing the hill town of Tel Jebeen.
The regime's undeterred offensive, backed by massive Russia air support, prompted British Foreign Secretary Philip Hammond to charge that Russian President Vladimir Putin is undermining the peace talks.
"It's a source of constant grief to me that everything we are doing is being undermined by the Russians," Hammond told Reuters in an interview. "The problem with the Russians is while they are talking they are bombing, and they are supporting [Syrian President Bashar al-Assad]."
Russia claims that its bombers are targeting "terrorist" groups like the Islamic State, which are not involved in the peace talks, but rebels and observers say they are killing hundreds of civilians in indiscriminate bombing.
"The Russians say they want to destroy Daesh, but they are not bombing Daesh. They are bombing the moderate opposition," Hammond said, using another term for Islamic State.
"Less than 30 per cent of Russian strikes are against Daesh targets," he said. "Their intervention is strengthening Daesh on the ground -- doing the very opposite of what they claim to be wanting to achieve."
With reporting by Reuters, AP, AFP, and dpa