At least 38 people have been killed in western Syria in a string of bomb attacks within territory held by the Assad regime, including near the major Russian naval base of Tartarus.

Two explosions – at least one of them caused by a suicide bomber – rocked the Syrian port city killing at least 30, according to state media, and injuring many more. Images shared on social media have shown a large black column of smoke rising into the sky near al-Arzunah bridge along the highway that runs parallel to the Tartarus base, Russias largest warm water naval facility abroad.

Reports say the first of the two explosions, caused by a car bomb, did not cause any casualties, however the second blast – caused by a suicide bomber – appears to have targeted crowds which gathered afterwards.

While no individual group has claimed responsibility for the attack, targeting civilians with secondary suicide bombers to cause maximum casualties is a tactic often employed by the Islamic State (Isis) militant group.

Two more explosions have also been reported in Homs, along the highway to Damascus. Homs health director told Syrian state media hospitals had received two bodies and seven injured people. The Syrian Observatory for Human Rights reported four soldiers were killed in the government-held Bab Tadmor district.

Syrian TV aired footage showing massive damage to the area, with a number of smashed cars and the bloodied body of a guard at the checkpoint, where the blast had taken place, according to the Associated Press.

In a third bomb attack, a motorcyclist detonated a bomb in the north-eastern city of Hasakeh, killing five, according to Syrian state media.

The attack on Tartus strikes deep within territory held by the Assad regime in what is essentially a green zone guaranteed by Russian military might. One of the principle reasons for Russias intervention in Syrias six-year civil war was to protect its military assets in western Syria, including Tartus, from which it projects power into the Mediterranean.

In May At least 100 were killed and some 200 injured after five explosions rocked Tartus and the coastal city of Jableh some 60 km to the north. Islamic State (Isis) later claimed responsibility for the devastating attacks.

Russia has fired a number of cruise missiles from its naval vessels based at Tartus at Isis targets. The Kremlins intervention in Syria in September 2015 has made Russia a primary target for Isis violence, as its backing of the government in Damascus essentially changed the course of the civil war.

The Russian President Vladimir Putin and his US counterpart Barack Obama met on Monday 5 September to discuss the crisis in Syria but were unable to come to any initial agreements. Their foregn ministers, Secretary of State John Kerry and Sergey Lavrov, had met ealier in efforts to negotiate a plan for cooperation between the two major military powers now involved in the conflict.