Bomb blasts and suicide attacks on Monday killed about 148 people in the Syrian coastal cities of Jableh and Tartous and over 40 in Yemen's capital Aden, news outlets and monitors said, in a government-controlled area that hosts Russian forces. Over 260 more were injured.
The Islamic State group claimed responsibility for the attacks in Yemen and Syria, saying it was targeting members of President Bashar al-Assad's Alawite minority. In the case of Syria, they attacked Mediterranean cities that have up to now escaped the worst of the conflict.
A second statement from the militant group said the attacks were carried out in a government-held area "so they experience the same taste of death which Muslims so far have tasted from Russian (and Syrian government) airstrikes on Muslim towns."
At least 120 were killed and scores were wounded in at least five suicide attacks and two car bombs, the Syrian Observatory for Human Rights said, the first assaults of their kind in Tartous, where government ally Russia maintains a naval facility, and Jableh in Latakia province, near a Russian-operated air base. State media confirmed the attacks but gave a lower death toll of 78. Amaq said 10 Islamic State members died in the attacks: 5 in Tartous and 5 in Jableh, according to the group's Amaq news agency.
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.
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.
The Kremlin said the blasts underscored the need to press ahead with peace talks after the collapse of a Feb. 27 ceasefire in April due to intensifying violence in a war that has killed at least 250,000 people.
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.
A suicide car bombing claimed by Islamic State group killed at least 40 army recruits and injured 60 others in the Yemeni city of Aden on Monday, medics said, in one of the deadliest attacks yet on the beleaguered government.
The attack occurred as the recruits lined up to enlist for military service at the home of a senior general in the Khor Maksar district of Aden, officials said.
The port city serves as the temporary capital of Yemen's Saudi-backed administration while it seeks to seize back the capital Sanaa from the armed Houthi group.
The attacks follow gains by Yemeni government forces backed by the United Arab Emirates, who mounted an offensive on al Qaeda militants in southern towns last month.
Al Qaeda in the Arabian Peninsula (AQAP) has taken advantage of chaos in Yemen since the civil war began to win control over swathes of southern and eastern Yemen.
Local news website Aden al-Ghad showed pictures of soldiers picking up bloodied comrades in uniform from the ground and witnesses reported seeing ambulances with blaring sirens collecting the wounded.
In a written statement posted to its social media accounts, the IS group said the attack targeted "the apostate Yemeni army" and named the attacker as Abu Ali al-Adeni.
The militant threat has spurred U.N.-sponsored peace talks between the Houthis and Hadi's government in Kuwait that have made little progress since they began last month.
The talks have been bogged down by differences over the implementation of a U.N. resolution calling for the Houthis to quit cities they control and hand over weapons and forming a more representative government.