Russian President Vladimir Putin has announced a ceasefire between Syrian opposition groups and the Syrian government starting at midnight on Thursday.

The parties were also prepared to start peace talks, Mr Putin said, after Moscow, Iran and Turkey expressed readiness to broker a deal to settle the nearly six-year-old Syrian war.

The Syrian army announced a nationwide halt to fighting but said Islamic State and ex-Nusra Front militants and all groups linked to them would be excluded from the deal.

A spokesman for the Free Syrian Army, a loose alliance of rebel groups, said it would abide by the ceasefire and take part in future talks.

It was the third nationwide ceasefire agreed in Syria this year.

The previous two, negotiated by Washington and Moscow, collapsed within weeks as warring sides accused each other of violations. The current deal does not involve the United States or United Nations.

The latest ceasefire deal follows a major defeat for the anti-Assad rebellion in Aleppo, where the Russian air force and Iranian-backed ground forces played a critical role helping the government drive rebels from eastern parts of the city.

Syrian President Bashar al-Assad (C-R) meeting with a joint delegation of MPs from the EU Parliament and the Russian upper house. Photo: AAP.

It also follows a thaw in ties between Russia and Turkey.

One rebel commander expressed optimism that this deal would be more effective.

“This time I have confidence in its seriousness. There is new international input,” said Colonel Fares al-Bayoush, an FSA commander, without elaborating.

Talks on the latest truce picked up momentum after Russia, Iran and Turkey last week said they were ready to back a peace deal.

Mr Putin said opposition groups and the Syrian government had signed a number of documents, including the ceasefire, measures to monitor the truce, and a statement on readiness to start peace talks.

The agreements reached are, of course, fragile, need a special attention and involvement… But after all, this is a notable result of our joint work, efforts by the defence and foreign ministries, our partners in the regions.”

Russia to reduce military deployment in Syria

Mr Putin also said Russia had agreed to reduce its military deployment in Syria.

Mr Putin spoke by phone to Assad who said he was committed to observing the ceasefire, the Kremlin said.

A street in Aleppo, Syria, taken in mid-December. Photo: AAP.

Turkey said it and Russia would guarantee the ceasefire.

“This window of opportunity should not be wasted,” Turkish President Tayyip Erdogan said.

Three rebel officials told Reuters the deal excluded Islamic State, but did include the Jabhat Fateh al-Sham group, formerly al Qaeda’s Syria branch, the Nusra Front – appearing to contradict the Syrian army’s statement.

The Free Syrian Army spokesman said the ceasefire also does not include the Kurdish YPG militia, which has mostly avoided conflict with the Syrian government.

The United States has been sidelined in recent negotiations and is not due to attend the next round of peace talks in Astana, capital of Kazakhstan, a key Russian ally.

However, Russian Foreign Minister Sergei Lavrov said the US could join the peace process once President-elect Donald Trump takes office next month.

Washington said the news of a ceasefire was a positive.

“We hope it will be implemented fully and respected by all parties,” State Department spokesman Mark Toner said.

The UN’s Syria envoy, Staffan de Mistura, welcomed the ceasefire announcement and hoped it would save civilian lives, enable the delivery of aid and lead to productive peace talks in Astana.