Russian President Vladimir Putin ratified an agreement with the Syrian government Friday that allows Moscow to use the Hmeimim air base in Syria indefinitely, the Kremlin said.

Putin's official signing off on the pact, that lasts for an "indefinite" period, is a legal move that paves the way for Moscow to make the base permanent. The air base and naval base near Tartus are Russia's strategic footholds in the Middle East.

Moscow is believed to have some 4,000 troops stationed at the Hmeimim air base with about a dozen warplanes. Its  naval base near the port city of Tartus is a holdover from Soviet times.

Civilian casualties mount

This comes as Syrian opposition activists are reporting intense airstrikes on rebel-held neighborhoods of the northern city of Aleppo amid clashes between government forces and rebels.

The UK-based Syrian Observatory for Human Rights on Friday reported dozens of overnight airstrikes on eastern Aleppo. It added that clashes are taking place on the northern and southern edges of the city.

The Observatory reported this week that at least 358 civilians have been killed in eastern Aleppo since a US and Russian-brokered truce broke down on September 19.

Rescue workers on the ground said that Syria's military backed by Russian warplanes had killed more than 150 people in eastern Aleppo this week alone, in support of its offensive against the city.

Rising casualties in what once was Syria's largest city but now largely in ruins, have prompted an international outcry and a renewed diplomatic push, withtalks between the United States and Russia planned for Saturdayin Lausanne, Switzerland.

'No special expectations' on Syria talks

Ahead of the meeting, Russian Foreign Minister Sergei Lavrorv said on Friday he has no specific expectations for the talks, as Moscow has yet to see reciprocal steps from its Western partners.

"I have no special expectations," he said as quoted by Russian news agency TASS. "We would like to work in a concrete way and to see first to what degree our partners are prepared to comply with UN Security Council resolutions."

Lavrov told reporters that Russia does not intend to propose new initiatives in resolving the conflict in Syria. Instead, Moscow intends to put forward suggestions on implementing the UN Security Council resolution. 

Foreign ministers from Turkey, Qatar, Saudi Arabia and Iran could also attend Saturday's talks.

Assad: Syrian conflict is a proxy war

Syrian President Bashar Assad is backed by the Russian military, Iran's Revolutionary Guards and an array of Shiite militias from Arab countries. The largely Sunni rebels seeking to oust him are backed by Turkey, the US and Gulf monarchies. In an interview this week, he said his country's conflict has evolved into a proxy war between major powers.

"What we've been seeing recently during the last few weeks, and maybe few months, is  something like more than Cold War," Assad told the Russian tabloid Komsomolskaya Pravda. "I don't know what to call it, but it's not something that has existed recently, because I don't think that the West and especially the United States has stopped their Cold War, even after the collapse of the Soviet Union."

Emboldened by Russian backing, he doubled down and said Damascus would drive foreign-backed insurgents seeking to oust his government. "You have to keep cleaning this area and to push the terrorists to Turkey, to go back to where they come from or to kill them. There's no other option," Assad told the Russian newspaper. "Aleppo is going to be a very important springboard to do this move."

Syria's civil war, now in its sixth year, has killed 300,000 people and left millions homeless while dragging in regional and global powers as well as inspiring jihadist attacks abroad.

rs, jar/kl (AFP, Reuters, AP)