Russia, Turkey and Iran will act as guarantors for a nationwide Syrian ceasefire deal reached between the government and rebels that goes into effect at midnight Thursday, Russian President Vladimir Putin announced.

The Syrian government and Turkish Foreign Ministry confirmed the truce. Syria's army said that the nationwide ceasefire would take effect at midnight local time (2200 GMT).

The truce excludes the Islamic State extremist militia, the formerly al-Qaeda-linked Fatah al-Sham Front and their affiliates, the Syrian army said in a statement.

"The decision to halt combat actions is aimed at providing favourable conditions to back the political course of the crisis in Syria," the army command said in a statement carried by Syria's state news agency Sana.

The ceasefire involves more than 60,000 rebels, Russian Defence Minister Sergei Shoigu said.

Russia, Turkey and Iran will help guarantee that the "fragile" ceasefire is observed, Putin said at a meeting with Shoigu and Foreign Minister Sergei Lavrov.

Russia, a key military ally of Damascus, also intends to reduce its military presence in Syria, according to Putin.

Lavrov expressed hope that the United States under Donald Trump, who will be inaugurated as president in January, will join the Russian-backed initiative in Syria.

The Syrian National Coalition, a main opposition grouping, welcomed the deal, urging rebel fighters to abide by the nationwide truce.

"The coalition calls on various opposition groups to implement the ceasefire agreement and foil any attempt by Iran and its militias to return to escalation," Samir Nashar, a member of the West-backed alliance, told dpa.

Iran and its allied Lebanese Hezbollah movement back the Syrian government in the conflict of more than five years.

"The Free Syrian Army (FSA) will abide by the truce, but it will retaliate against any breach," Nashar added, referring to the armed wing of the coalition.

Under the deal, Russia and Turkey are to propose a monitoring mechanism for the ceasefire, Mohammed al-Shami, a senior FSA commander, said.

"The guarantors will make sure that no party to the conflict will try to seize new areas," al-Shami told dpa.

"Negotiations will be launched within a month after the ceasefire takes effect with the aim of reaching a political solution," he added without details.

Russia and Turkey have supported opposing sides in the Syrian civil war, but in recent months, amid a rapprochement in their relations, have ramped up efforts to seek a peaceful resolution to the conflict.

The latest ceasefire comes a week after Syrian forces regained full control of Aleppo after a Russia-backed campaign forced rebel fighters to leave their last enclave in the northern city.

Syria's conflict started in March 2011 with a crackdown on mostly peaceful anti-government protests.

World powers have since made numerous attempts to end the war. Past truces have largely held only for brief periods, allowing in some humanitarian aid or letting people flee.

Some local ceasefires have been more successful.

- dpa