Islamic State militants say they are behind a string of deadly bomb attacks that have killed at least 119 people in Homs and near Damascus in Syria.

At least 57 people were killed and 100 others wounded in twin car bomb blasts that hit Homs in one of the deadliest attacks in the city in five years of civil war, the Britain-based Syrian Observatory for Human Rights said.

Later, another 62 people were killed in a triple suicide attack, including a car bombing, near the Shiite shrine of Sayyida Zeinab south of Damascus, the Observatory said.

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Witnesses say suicide bombers blew themselves up after detonating a car bomb.

State media had earlier put the Damascus death toll at 30.

Islamic State militants have claimed all of the attacks in online statements.

The attacks came a day after government advances against the Islamic State group.

State television footage from Homs showed charred corpses buried among rubble, damage to shop fronts and debris littering a wide area.

Many cars were on fire, sending out plumes of black smoke. Wounded people walked around dazed.

The attack was the worst since twin blasts in October 2014 hit a school, killing at least 55 people, including 49 children.

A bomb attack claimed by Islamic State militants last month in Homs killed at least 24 people as government forces took back some Islamic State-held villages in Aleppo province in the north.

Violence rages on unabated across the country as world powers and the United Nations push to end the conflict, meeting in Geneva to try to broker a ceasefire.

Peace talks were suspended almost immediately earlier this month as Syrian government forces and their allies, backed by Russian air strikes, intensified assaults against insurgents in Aleppo province.

The latest fighting in the north of the country has displaced tens of thousands of people, many of whom headed for the Turkish border.

The exodus added to more than 11 million already displaced by the conflict that has claimed 250,000 lives.