Istanbul - A female cleaner was killed and another wounded early Wednesday after an explosion of unknown origin beside a plane at Istanbul's second international airport, with Turkey on high alert for possible attacks.
Airport cleaner Zehra Yamac, 30, died of head wounds hours after the pre-dawn blast on the tarmac at Sabiha Gokcen airport on the Asian side of Turkey's largest city, the state-run Anatolia news agency reported.
The explosion took place just outside the terminal building where planes park for their passengers to embark and disembark.
Turkey's private carrier Pegasus Airlines said in a statement the explosion took place next to one of its planes on the tarmac while the two cleaners were nearby.
"There were no passengers either on the plane or on the stairway. Sabiha Gokcen airport is continuing its normal operations," Pegasus said.
The wounded victim, also a cleaner, was hurt in the leg. Yamac was hospitalised but died of her wounds despite the efforts of medical staff, Anatolia said.
The airport said in a statement on its official Twitter account that "flights from our terminals are continuing according to schedule."
Sabiha Gokcen airport, named after Turkey's first female fighter pilot, is the second international airport in Istanbul after much larger Ataturk Airport on the European side of the city.
Sabiha Gokcen hosts flights both to domestic and numerous international destinations often with budget airlines but also from Turkey's flag carrier Turkish Airlines.
In 2015, up to November, it hosted over 17 million domestic passengers and almost nine million international passengers, according to company figures.
It is now fully owned by Malaysian Airports Holding which completed the acquisition of the remaining shares in the airport this year.
"We are working very closely with the Turkish government and our counterparts to facilitate the investigation, and we await their official report on it," Dato' Azmi Murad, the executive director of Sabiha Gokcen said in a statement.
"The Turkish government has heightened security within the vicinity of the airport, which includes helicopter surveillance," he added.
According to Azmi, the airport resumed "normal flight operations" around two hours after the blast.
The Dogan news agency said that three planes up to 350 metres (1,150 feet) away from the site of the blast had sustained damage.
Police stepped up security at airport entrances after the blast, searching vehicles while a police helicopter circled overhead, Anatolia said.
That attack was blamed on Islamic State (IS) jihadists, like two other deadly strikes in the country's Kurdish-dominated southeast earlier in the summer.
Turkish authorities have in recent weeks detained several suspected IS members with officials saying they were planning attacks in Istanbul.
But Turkey is also waging an all-out assault on the outlawed Kurdistan Workers' Party (PKK) which has staged dozens of deadly attacks against members of the security forces in the southeast of the country.
Meanwhile the banned ultra-left Revolutionary People's Liberation Party-Front (DHKP-C) has also staged a string of usually small-scale attacks in Istanbul over the last months.