Bomb blasts killed nearly 150 people and wounded at least 200 in Jableh and Tartous on Syria's Mediterranean coast on Monday in the government-controlled territory that hosts Russian military bases, monitors and state media said.

Islamic State claimed responsibility for the attacks in the cities that have up to now escaped the worst of the violence in the five-year-old conflict, saying it was targeting members of President Bashar al-Assad's Alawite minority.

Open gallery view A map showing Syria's coastal Alawite enclave. Credit: Haaretz

The Britain-based Syrian Observatory for Human Rights said 148 people were killed in attacks by at least five suicide bombers and two devices planted in cars. State media had said 78 people had been killed in what is Assad's coastal heartland.

The attacks were the first of their kind in Tartous, capital of Tartous province and home to a Russian naval facility, and in Jableh in Latakia province, near a Russian-operated air base.

The Kremlin said the bomb blasts underscored the need to press ahead with Geneva peace talks after the collapse of a February 27 cease-fire in April due to intensifying violence in a war that has killed at least 250,000 people.

Open gallery view Syrians gather at the site of multiple bombings that left dozens dead in the northern coastal city of Jableh, between Latakia and Tartus, Syria, May 23, 2016. Credit: Stringer, AFP

"This demonstrates yet again just how fragile the situation in Syria is. And this one more time underscores the need for new urgent steps to continue the negotiating process," Kremlin spokesman Dmitry Peskov told a conference call with journalists.

Russian President Vladimir Putin reiterated his readiness to fight with the Syrian government against "the terrorist threat" and sent his condolences to Assad, the Kremlin said.

The Syrian foreign ministry sent a letter to the United Nations, state television reported, saying the blasts were a "dangerous escalation by the hostile and extremist regimes in Riyadh, Ankara and Doha," referring to support given to the rebels by Saudi Arabia, Turkey and Qatar.

UN Secretary General Ban Ki-moon condemned the attacks and a spokesman said Ban took "note with great concern of the escalating military activity in many areas in and around Damascus."

"Blood and bodies"

One of the four blasts in Jableh happened when a man walked into a hospital emergency department and blew himself up. Another blast was at a bus station. The Tartous bombs also targeted a bus station, the Observatory and state media said.

Younes Hassan, a doctor working at the Jableh hospital, said he heard an explosion at the bus station, followed less than a minute later by the blast at the hospital.

"Everything went into emergency mode, wounded people began arriving," he told Reuters by phone.

The Tartous explosions also occurred in quick succession, no more than 10 seconds apart, a driver at the bus station said.

"People began running but didn't know which direction to go, cars were on fire, there was blood and bodies on the ground," Nizar Hamade said.

Footage broadcast by the state-run Ikhbariya news channel showed several twisted and burnt-out cars and minivans.

Islamic State claimed the attacks in a statement posted online by the group's Amaq news agency, saying its fighters had targeted "gatherings of Alawites."

Syria's Information Minister Omran al-Zoubi said in an interview with Ikhbariya that terrorists were resorting to bomb attacks against civilians instead of fighting on the front lines, and vowed to keep battling them.

The government refers to all insurgents fighting against it in the conflict as terrorists.

The Observatory said an area of Tartous hosting internally displaced Syrians near a blast site was briefly attacked by government supporters in reaction to the bombings. Some tents were burned but nobody was killed.

Tartous governor Safwan Abu Saadah told Reuters that reports on social media about refugees being shot and tents being burned down were not true. He said some Tartous residents had gone to refugee areas to protect them from possible attacks.

"Two days ago some camps in Tartous province experienced fires because of electrical problems ... today's reports that people burned (these camps) are not true. Nobody would turn against our guests in this way," Abu Saadah said.

Bombings in the capital Damascus and western city of Homs this year killed dozens of people and were also claimed by Islamic State, which is fighting against government forces and their allies in some areas, and separately against its jihadist rival al Qaeda and other insurgent groups.

Latakia city, which is north of Jableh and capital of the province, has been targeted on a number of occasions by bombings and insurgent rocket attacks, including late last year.

Government forces and their allies have recently stepped up bombardment of areas in Aleppo province in the north, which has become a focal point for the escalating violence. Insurgents have also launched major attacks in that area.

The only road into rebel-held areas of Aleppo city has suffered a week of increasingly heavy air strikes. Zakaria Malahefji, a senior official in the rebel group Fastaqim that operates in the Aleppo area told Reuters that the road was heavily bombarded again on Monday and was dangerous to use.

He said Iranian-backed fighters, who are supporting government forces, were mobilising in the southern Aleppo area.

France's foreign ministry called the Tartous and Jableh bombings "odious," and said violence from all sides must stop if a political transition is to take place.