Blast kills 11 in north-western Syria
The bombing took place in Jisr al-Shoughour area, activists said.
The Britain-based Syrian Observatory for Human Rights, said the explosion took place near an office that belonged to the al-Qaeda-affiliated Hayat Tahrir al-Sham alliance.
The observatory, which has been monitoring violence in Syria since the uprising started in 2011, said at least 28 people were also injured.
The province of Idlib is largely controlled by Hayat Tahrir al-Sham as in the past few years Russia, a key ally of Damascus sponsored deals between the government and hardline rebels to transfer them to Idlib.
In September, Russia and Turkey, which supports some rebel groups in Syria, reached a deal to establish a demilitarised buffer zone in the Idlib enclave, a move that prevented a major government offensive there.
The buffer zone includes parts of the neighbouring provinces of Latakia, Hama and Aleppo.
Meanwhile, a car bomb exploded south of the capital Damascus, killing one person and wounding three, a Syrian police source told dpa.