At least seven people were killed and more than 20 people wounded in rebel-held Azaz in Syria late on Saturday in a car explosion at a busy marketplace.

The blast took place during peak late-night shopping hours during the daytime fasting holy month of Ramadan.

"It's timing comes with heavy congestion by shoppers," Yaseen Shalabi, who was near the site of the explosion with his family, told the Reuters news agency.

No group immediately claimed responsibility for the blast.

Initial casualty figures varied slightly, with between seven and eight killed and between 23 and 30 injured.

Some of the wounded were seriously hurt and were taken to nearby hospitals.

The blast caused considerable material damage and also secondary fires, officials reported.

Emergency services and investigators were on site tending to the wounded and seeking first clues by torchlight.

Azaz, a rebel-held town near the Turkish border in northwest

The Syrian town of Azaz, north of Aleppo near the border with Turkey, is not under the control of President Bashar al-Assad's regime.

The predominantly Arab-populated town is run by Syrian rebel groups opposed to Assad and backed by Turkey.

Azaz was hit by a car blast two years ago but has been comparatively calm since, by the standards of Syrian northern border regions during the country's civil war that started in 2011.

Larger towns in the northwest have seen similar attacks more frequently.

Residents and rebels in the region have long suspected the Kurdish-led YPG, and who control much of nearby northeastern Syria. The YPG, however, denies such claims.

Turkey, which considers the YPG allies of the outlawed insurgent Kurdistan Workers' Party (PKK), and its Syrian proxies have launched successive military offensives in the region, mainly against Kurdish fighters.