A string of bomb blasts hit mostly regime-controlled areas of Syria on Monday, killing at least 42 people and wounding dozens more, local media said.
The blasts hit regime-held Tartous and Homs, as well as Hasakeh, which is mostly controlled by the PKK's Syrian affiliate YPG.
Regime media said at least 30 people had been killed and 45 injured in a double bomb attack just outside the city of Tartous, in the coastal province of the same name, which is a stronghold of Bashar al-Assad's regime.
A car bomb exploded on the Arzuna bridge followed by a suicide bomber who detonated his explosive belt when people gathered to help the wounded, Syrian regime television said.
No individual or group claimed responsibility for the attacks.
Tartous, which also hosts a Russian military base, has largely been spared the worst violence of Syria's conflict since it began with pro-democracy protests in March 2011.
Bab Tadmor, Homs - SANA pic.twitter.com/wAOZTxImcu
— Hassan Ridha (@sayed_ridha) September 5, 2016
Regime media also reported that eight people were killed in a bombing in Hasakeh, in the northeast of the country.
The Syrian Observatory for Human Rights, a Britain-based monitor, said the blast hit a checkpoint under the control of the YPG.
Hasakeh city has been regularly targeted by DAESH, including in July, when a bomber on a motorcycle killed at least 16 people outside a bakery in the city.
The terrorist group has been losing ground to the US-backed Syrian Democratic Forces, which is mainly comprised of the YPG, even though its affiliate organisation, the PKK, is listed as a terrorist organisation by Turkey, the US and the EU.
More recently, DAESH has also lost territory to Turkish-backed Free Syria Army (FSA) fighters. Over the weekend, advances by the Turkish Army and Free Syria Army (FSA) fighters expelled DAESH from the last stretch of the Syrian-Turkish border under their control.
Turkish Armed Forces launched Operation Euphrates Shield on August 24 to protect its borders and secure the Turkish town of Karkamis, adjoining Syria, from DAESH attacks.
In central Homs city, regime media said at least three people were killed in a car bomb at the entrance to the Al-Zahraa neighbourhood, whose residents mostly belong to the same Alawite sect as Assad.
Al-Zahraa has also been regularly targeted in bomb attacks, including a devastating double bomb blast in February that killed 57 people and was claimed by DAESH.
Regime television broadcast images from the aftermath of the blast in Homs, showing rubble strewn on the streets and smoke rising from the charred remains of vehicles.
Another bomb attack was also reported on the Al-Sabura road west of the capital Damascus, with regime media saying one person had been killed and three injured in that bombing.
The Observatory said that the attack targeted a checkpoint and gave a death toll of three.
Observatory director Rami Abdel Rahman said the blasts appeared to be coordinated.
"Clearly these attacks were simultaneous and they all targeted security posts," he told AFP.
More than 290,000 people have been killed in Syria since the war started, and millions have been displaced by the fighting.
Successive rounds of international negotiations aimed at finding a political solution have failed to bear fruit, but US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov are due to resume discussions on stemming the violence on Monday.