Story highlights

NEW: "The situation is tense," a Yemeni government official says

It is not clear what set off the explosion

There are no immediate reports of injuries

Flights to Sanaa are being rerouted to Aden

Sanaa, Yemen CNN  — 

Flames and thick black smoke filled the skies above Sanaa International Airport on Sunday after an explosion struck a nearby air base, senior officials said.

Flights to Sanaa are being rerouted to Aden, according to an airport official.

It was not immediately clear what caused the explosion.

Two senior security officials at the airport said a mortar shell landed at Dailami air force base, two miles west of the airport, provoking a massive blast.

However, a senior official with the Interior Ministry said the explosion was caused by a bomb planted near the airport. He declined to speculate who could have been behind the attack.

And separately, a Yemeni government official said both the air base and airport were shelled.

“The situation is tense. The airport and air base were shelled by rebels,” said the official, who was not authorized to speak to the media.

There were no immediate reports of injuries.

“The explosion was strong and flames are strong at the area of the attack. If it was a mortar, it would cause an explosion and not massive flames,” said the Interior Ministry official, who was also not authorized to speak to the media.

CNN’s Mohammed Jamjoom contributed to this report.