Russia's President Vladimir Putin said the only way to end the war in Syria is to support its existing government in the fight against terrorism, in remarks released Thursday.

In an interview with CBS News "60 Minutes," the Russia leader repeated his view that only the Syrian people can decide if and when to replace President Bashar Assad.

Foreign Minister Jebran Bassil has said that the Syrian refugee crisis has had very harmful effects on Lebanon's security and economy.

“This crisis had catastrophic effects on security, development, the economy, the society and the environment,” Bassil said in a speech he gave at the Group of 77 and China meeting that was held in New York.

More than 150,000 trained and equipped fighters in pro-government groups, including Hizbullah, have become an indispensable brace for a Syrian army beleaguered by well over four years of intractable conflict.

"There are more than 25 main militias of different sizes that fight alongside the Syrian army" and number between 150,000 and 200,000 men, a security source told Agence France Presse.

The United States and Russia could find ways to cooperate on the crisis in Syria, Pentagon chief Ashton Carter said Thursday, as Moscow continues a military build-up in the war-torn nation.

Carter said if Russia were to pursue a political solution to the four-and-a-half-year Syrian crisis, and not just "indiscriminately" attack foes of President Bashar Assad, "we could find areas of cooperation."

Turkish President Recep Tayyip Erdogan, a fierce critic of Bashar Assad, on Thursday suggested for the first time that the Syrian president could have a role to play in a future political transition.

"The process could possibly be without Assad, or the transitional process could be with him," Erdogan told reporters after Eid prayers in Istanbul, when asked about a possible solution to Syria's four-year civil war.

Hizbullah and Syrian rebels have reached an agreement involving a six-month ceasefire in three battleground Syrian towns, a monitoring group said Thursday.

“Under Turkish and Iranian sponsorship and with guarantees from the United Nations, an agreement has been reached between Lebanon's Hizbullah and the fighters of Zabadani and the Islamist Ahrar al-Sham movement in Zabadani, Fuaa and Kafraya,” the anti-regime Syrian Observatory for Human Rights announced.

Russia and the United States have reached a "tacit agreement" on ending Syria's bloody crisis, a senior adviser to Syrian President Bashar Assad has said.

"The current U.S. administration wants to find a solution to the crisis in Syria. There is a tacit agreement between the U.S. and Russia to reach this solution," Bouthaina Shaaban said in an interview with state television late Wednesday.

The truck with 71 dead migrants abandoned in August on an Austrian motorway had Hungarian plates and a Slovakian poultry firm's livery. But five of the six suspects since arrested are Bulgarians.

To detectives probing the dark business of human trafficking, this was no surprise. 

NATO head Jens Stoltenberg told Agence France Presse Thursday he was concerned by Russia's "substantial" military build-up in Syria and urged Moscow to play a constructive role in the fight against Islamic State jihadis.

"It underlines the importance of Russia making clear what are their intentions," Stoltenberg told Agence France Presse in an interview at NATO HQ in Brussels.

Britain's government is facing a legal challenge Thursday over its use of a drone to kill two British Islamic State (IS) group jihadists in Syria, even though it is not part of military action there.

Prime Minister David Cameron announced this month that a British drone had killed two British jihadists and another unidentified militant in the group's stronghold of Raqqa in August.