Russian Foreign Minister Sergei Lavrov is set to meet US Secretary of State John Kerry, as well as their Turkish and Saudi counterparts, in Vienna on Friday for crucial talks on the Syrian conflict, a four-year war that has killed more 250,000 people and forced millions from their homes.
The high-level meeting follows the surprise visit of Syrian President Bashar al-Assad to Moscow for talks with Putin on Tuesday, the embattled leader's first foreign visit since 2011.
Russia -- which has pledged to support Damascus militarily, much to the West's dismay -- has insisted the air strikes it has conducted since September 30 in the war-torn country are hitting the Islamic State and other "terrorist" groups, and are being conducted at the Syrian leadership's request.
But the US and its allies, who are conducting a separate bombing campaign in the country, say Moscow's strikes are aimed at Western-backed moderate rebels fighting Assad.
"There is no need to play on words, to classify terrorists are moderate and non-moderate," Putin said.
"What is the difference?" he said, suggesting that "in the opinion of some experts... so-called moderate bandits behead people moderately or gently."
During his encounter with Assad, Putin called for a political solution involving all groups to try to end the war, the Kremlin said.
Kremlin spokesman Dmitry Peskov later declined to comment on whether Assad's future in Syria had been discussed during the encounter.
Assad, who last visited Russia in 2008, told Putin that the three-week Russian bombing campaign had helped to stop the spread of "terrorism" in his country.
- Destroyed 'combat capability' -
While the Syrian leadership sang the praises of Moscow, the White House castigated Russia's intervention, calling it "counterproductive".
Russia's defence ministry said Thursday it had struck 72 "terrorist" targets in Syria over the past 24 hours, claiming to have destroyed the combat capability of the main terrorist groups operating in the country.
"As a result of Russian air strikes, the main forces of terrorist groups, made up of the best trained terrorists, have lost combat capability. Their command and resupply system has been disrupted," senior military official Andrei Kartapolov told Russian news agencies.
Kartapolov said the strikes -- which targeted the provinces of Hama, Idlib, Latakia, Damascus, Aleppo and Deir Ezzor -- had destroyed a bridge over the Euphrates River used for moving supplies to fighters from neighbouring Iraq.
Putin said that strikes had given a "positive result" but added: "Is it enough to be able to say that terrorism in Syria is defeated? No, we need to make more serious efforts in order to make such a claim."
Russian Foreign Ministry spokeswoman Maria Zakharova denied Thursday an earlier report by the Syrian Observatory for Human Rights that at least 12 people including medical staff were killed when Russian warplanes struck a field hospital in the northwestern province of Idlib.
The Russian strikes are reported to have killed 370 people so far, a third of them civilians, the Britain-based monitoring group said Tuesday.
Humanitarian organisations have condemned the bombing campaigns, with the International Committee of the Red Cross saying air strikes in Syria were disrupting the delivery of desperately needed aid to civilians.
Since the start of Moscow's intervention, Russian planes have carried out 934 sorties that have destroyed 819 "terrorist targets", Kartopolov said.
Britain, France and Spain will soon present a draft resolution to the UN Security Council on stopping the Syrian regime from using barrel bombs.
French ambassador Francois Delattre told the 14-member council that barrel bombs were a "weapon of terror" that were fuelling the exodus of refugees to neighbouring countries and to Europe.
Human rights groups say barrel bombings by the regime are the number one killer in the four-year war, claiming more civilian lives than IS attacks.
But it remains highly unlikely that Russia would support such a measure.