BEIRUT — Bombings claimed by the Islamic State in the Syrian cities of Damascus and Homs killed nearly 130 people Sunday, highlighting the threat posed by the extremists as the country’s warring factions fight for the northern city of Aleppo and world powers chase an elusive cease-fire.

The blasts came as Secretary of State John Kerry said that a “provisional agreement” has been reached on a cessation of hostilities that could begin in the next few days. But he acknowledged that it’s not finalized and all parties might not automatically comply.

A series of blasts ripped through the Sayyida Zeinab suburb of Damascus, killing at least 83 people and wounding more than 170, the official SANA news agency said. The Britain-based Syrian Observatory for Human Rights, which relies on local Syrian activists, said the blasts killed 62. SANA said the bombs went off near schools during the afternoon rush hour.

The neighborhood is home to one of Shiite Islam’s holiest shrines, which his heavily guarded by Lebanon’s Hezbollah movement and other Shiite militiamen from Iraq and elsewhere. Hezbollah’s Al-Manar TV said the blasts were caused by a car bomb and two suicide bombers.

The bombings in the central city of Homs killed at least 46 people and wounded dozens, according to Syria’s Foreign Ministry. The Observatory said 57 people, including 11 women, were killed by two car bombs set off in a mostly Alawite neighborhood. Syrian President Bashar Assad hails from the Alawite minority, an offshoot of Shiite Islam.

The Islamic State claimed both attacks. The extremists are dug in on the outskirts of the two cities and have repeatedly targeted Shiites, who they view as apostates deserving of death.

The deadly blasts may strengthen the government’s argument that it should press ahead with a major offensive in the north of the country, where troops backed by Russian airstrikes are close to sealing off Aleppo, once Syria’s largest city. Syrian insurgents, including Western-backed rebels, seized several neighborhoods in 2012.