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At least four people were injured in an overnight blast in the Turkish district of Maltepe in Istanbul, state-run Anadolu news agency reported on Monday.

A homemade device planted under an overpass on the Asian side of the city exploded, wounding two passengers in a car and two pedestrians waiting for a taxi. All four were hospitalised.

Other passing vehicles were also damaged by flying pieces of metal.

There was no immediate claim of responsibility for the blast, but Kurdish and Islamic State militants have previously carried out attacks in Istanbul, as well as Turkey's capital Ankara and other cities across the country.

Turkey has come under major security threats, including a blowback from war-torn neighbouring Syria as well as renewed conflict with Kurdish militants in the southeast.