Russian investigators on Sunday blamed a defective brake system for a Moscow airport crash that killed five crew members when a liner skidded off the runway and smashed into a highway.

Rescue workers recovered the flight recorders from the four-year-old Tu-204 of tycoon Alexander Lebedev's Red Wings airlines late Saturday as Russia began mourning its latest post-Soviet crash fatalities.

Four crew were killed Saturday when a Russian airliner crashed into a motorway and broke up into three pieces after overshooting the runway at an international Moscow airport.

The Red Wings airlines Russian-made Tu-204 jet -- empty of passengers and carrying just its eight crew on a return trip from the Czech Republic -- caught fire after crashing through the perimeter fence of Vnukovo airport in the west of the city.

Russia acknowledged on Saturday that Syrian President Bashar Assad will not be persuaded to quit but insisted there is still a chance of finding a political solution to the 21-month conflict.

International peace envoy Lakhdar Brahimi warned Syria was facing a choice between "hell or the political process" after talks with Russian Foreign Minister Sergei Lavrov on his end-of-year bid to accelerate moves to halt a conflict that monitors say has now killed more than 45,000 people.

U.N.-Arab League peace envoy Lakhdar Brahimi stressed on Saturday that Lebanon can no longer support the large influx of Syrian refugees fleeing the crisis in neighboring Syria.

“The problem can no longer be ignored,” Brahimi said during a joint press conference with Russian Foreign Minister Sergie Lavrov in Moscow.

The head of Syria's mainstream opposition National Coalition on Friday rejected an invitation by Moscow for talks to find a solution to the 21-month-old conflict, accusing Russia of interference.

"We have said frankly that we will not go to Moscow," Ahmed Moaz al-Khatib told al-Jazeera television.

The United States on Friday expressed deep regret after Russian President Vladimir Putin signed a tough anti-U.S. adoption law, and said it hoped adoption cases already under way would not be affected.

"We deeply regret Russia's passage of a law ending inter-country adoptions between the United States and Russia," State Department spokesman Patrick Ventrell said in a statement, decrying the move as "politically motivated".

Japan's new Prime Minister Shinzo Abe agreed with Russian President Vladimir Putin Friday to restart talks on a peace treaty hampered since World War II by a territorial row, an official said.

In a 20-minute telephone conversation, Abe, who was formally elected to his second stint as Japan's premier on Wednesday, also agreed to visit Russia at an "appropriate" date in 2013, the Japanese official said.

Russian investigators on Friday questioned the country's ousted defense minister as part of one of the most high-profile corruption probes of President Vladimir Putin's 13-year rule.

The powerful Investigative Committee interrogated former defense minister Anatoly Serdyukov for about an hour as part of an inquiry into a suspected $100 million property scam.

A Moscow court on Friday acquitted a former top prison official accused of negligence over the death in detention of lawyer Sergei Magnitsky in 2009, a tragedy that sparked a diplomatic scandal with the United States.

Magnitsky died in horrible pain at only 37 as he was under arrest over a fraud probe. He was jailed after testifying against interior ministry officers and accusing them of embezzling $235 million paid as taxes by his client.

President Vladimir Putin on Friday signed into law a ban on the adoption of Russian children by American families that activists slammed for making orphans pawns in a diplomatic row between Moscow and Washington.

The law -- retaliation for a U.S. law punishing Russian officials implicated in the 2009 prison death of the whistle-blowing attorney Sergei Magnitsky -- will take effect on January 1, the Kremlin said in a statement.