Authorities in Istanbul have banned transgender and gay pride marches this month, citing security concerns after ultra-nationalists warned they would not allow "degenerates" to hold the events on Turkish soil.

A march in support of transgender people was planned for Sunday in central Istanbul, while an annual gay pride parade - described in the past as the biggest in the Muslim world - had been due to take place a week later on June 26.

The Istanbul governor's office said on Friday the marches had been banned out of concern for public order. Security in the city is already tight after a series of bombings blamed on Islamic State and Kurdish militants in recent months.