BEIRUT (AFP) - A fuel truck bomb killed 46 people including at least six Turkey-backed rebel fighters on Tuesday (April 28) in a northern Syrian city controlled by Ankara's proxies, a war monitor said.

The explosion of a bomb in a fuel truck in a market in Afrin killed "at least 46 people, including civilians, and wounded 50 others," according to Rami Abdul Rahman, the head of the Britain-based Syrian Observatory for Human Rights.

Updating an earlier toll, he said the number could climb still further as some of the wounded were in critical condition.

At least six pro-Turkish Syrian fighters were among the dead, he added.

It was not immediately clear who was behind the blast, one of the largest to rock Afrin since Turkish troops and allied rebels seized the region from Kurdish forces in March 2018 after a two-month air and ground offensive.

The Turkish defence ministry blamed Tuesday's attack on the Kurdish People's Protection Units (YPG) which it views as a "terrorist" offshoot of the outlawed Kurdistan Workers' Party (PKK).

"The enemy of humanity PKK/YPG has once again targeted innocent civilians in Afrin," the Turkish ministry said on Twitter.

The PKK has been waging a bloody insurgency in Turkey for three decades.

In January, at least seven people were killed in a car bomb in Azaz, another northern city held by pro-Turkey forces, according to the Observatory, which relies on a network of sources inside Syria.

The Syrian conflict has killed more than 380,000 people since 2011 and forced more than half of the country's pre-war population from their homes.