ISTANBUL (Reuters) - One person was killed when an explosion hit an Istanbul airport overnight and damaged five planes, a Turkish minister said, adding that it was still too early to confirm whether the blast had been caused by a bomb.

The blast at Sabiha Gokcen, the city’s second airport and located on its Asian side, occurred shortly after 2:00 a.m. (midnight GMT), local budget carrier Pegasus said, fatally wounding a cleaner on one of its planes.

“There was damage to five airplanes in total due to the impact of shrapnel. Weakness in the airport’s security is out of the question. All international security standards are being implemented,” Transportation Minister Binali Yildirim told reporters.

“On the cause of the incident, security and intelligence teams are carrying out investigations. But it’s too early to reach a verdict or comment on it yet.”

Bomb attacks by Kurdish, leftist and Islamist militants are common in Turkey. A three-decade-old conflict between the state and the militant Kurdistan Workers Party (PKK) has flared up in the mainly Kurdish southeast since the collapse of a ceasefire in July.

The airport’s owner, Malaysia Airports, referred to more than one explosion “at the tarmac area”, adding that normal flight operations had resumed by 0200 GMT.

No passengers were in the area at the time of the airport blast.

A photo on Dogan news agency’s website showed a hole in one plane window. Video footage showed investigators taking photos of a terminal building wall, dozens of metres from the nearest planes.

Police armed with rifles and protective vests imposed tight security at entrances to the airport, searching vehicles while a police helicopter circled overhead, state-run Anadolu Agency said.

Sabiha Gokcen served around 26 million passengers in the first 11 months of the year, its website said, less than half the number at the main Ataturk airport on the European side of the city.