A derby between bitter Istanbul rivals Galatasaray and Fenerbahce was postponed Sunday over a “serious” threat, authorities said, a day after a suicide bomb attack in the Turkish city killed four people.

“The football match was postponed in light of serious information” pointing to the risk of an attack, the local governor’s office said in a statement less than two hours before kick-off.

The governor took the decision following a meeting with sporting authorities, news channels CNN-Turk and NTV said.

Spectators had already started arriving for the game at Galatasaray’s Turk Telecom Arena on the European side of the Bosphorus when the decision was announced and they were asked to leave the ground.

Three Israelis and one Iranian were killed, and 39 people injured, when a bomber blew himself up Saturday on Istiklal Caddesi, a bustling pedestrian street and popular meeting spot in the heart of the Istanbul.

No group has claimed responsibility for the attack, but Turkey’s Interior Minister Efken Ala said Sunday that the perpetrator was a Turkish jihadist with links to the Islamic State.

The decision to call off the game between Galatasaray, who lay fifth in the Turkish Super Lig, and second-placed title challengers Fenerbahce came despite authorities calling for the 15 million inhabitants of Turkey’s largest city to carry on with life as normal after the blast.

The attack was the latest in a series of terrorist attacks that have hit the country in recent months, including a suicide car bombing in a busy square in the capital Ankara last weekend which killed 35 people.