“The explosion occurred at the first checkpoint of Kabul airport,” said deputy Kabul police chief Sayed Gul Agha Rouhani.
Smoke billowed from the scene of the explosion, where passengers undergo the first round of body checks before entering the airport.
Ambulances with wailing sirens rushed to the area and were seen removing bodies.
Early reports suggest 4 were killed and 18 others were wounded in the incident.
No group immediately claimed responsibility for the attack, which comes after a wave of lethal bombings in the capital on Friday as the insurgency escalates following a bitter power transition within the Taliban.
The blasts on Friday struck near an army complex, a police academy and a US Special Forces base, killing at least 51 people, officials said.
They were the first major attacks since Mullah Akhtar Mansour was named as the new Taliban chief last week in an acrimonious power transition after the insurgents confirmed the death of longtime leader Mullah Omar.
The wave of violence underscores Afghanistan’s volatile security situation amid a faltering peace process.