The Edlib Media Centre, an activist collective, said the bombings killed 13 and wounded dozens.
The Syrian Observatory of Human Rights said the blasts in the Qusour neighbourhood during rush hour killed 17 people and wounded about 50.
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The first blast occurred in the early afternoon and another followed seconds later.
The city of Idlib is controlled by al-Qaida-linked Hayat Tahrir al-Sham, which has wide influence in northern Syria.
The city has been hit with bombings in recent months that killed or wounded scores of people.