An explosion near a secondary school killed three people, injured at least other 15 and set several vehicles on fire in the Turkish capital, Ankara, on Tuesday.

It was not immediately clear what caused the blast in the downtown Kizilay district but a deputy prime minister said a bomb was suspected.

According to Besir Atalay, Turkey’s deputy prime minister, there was “information that a bomb was planted” on a vehicle.

Five of the injured people are in critical condition, Besir Atalay said.

The explosion killed three people, injured at least other 15 and set several vehicles on fire in Ankara

The vehicle detonated across from the district governor’s office and about 200 meters (650 feet) from Prime Minister Recep Tayyip Erdogan’s office.

“I’ve learned that people who haven’t got any sense of humanity terrorized civilians and carried out an attack in Ankara,” President Abdullah Gul said in televised comments from Germany, where he is on a state visit.

 “I strongly and vehemently curse this act of terrorism.”

Thick smoke could be seen rising from the central commercial area of Kizilay.

According to local mayor, Bulent Tanik, an eyewitness saw one person throwing a burning gas canister on to the vehicles from a nearby building.

“The investigation is under way,” Bulent Tanik said. “If true, that canister might have triggered the blast of a liquefied petroleum gas tank on a vehicle.”

The blast was powerful enough to destroy six cars and shatter windows in Kizilay, which is surrounded by government ministries. One of the vehicles was totally burnt down, television images showed.

Interior Minister Idris Naim Sahin said the initial blast, in an LPG-fueled car, triggered five other similar vehicles on the street to explode. The first car to detonate was sold September 13 and the transaction hadn’t yet been completed, he said.

IdrisNaim Sahin said it was “highly likely to be a terrorist attack”. Kurdish, leftist and Islamic militants have carried out bomb attacks in Turkey in the past.

Interior minister said the attackers wanted to target as many people as possible, because the street where the blast occurred was normally very busy.

A fire broke out but was quickly contained by firefighters. Several vehicles were damaged and windows were blown out in nearby buildings.

Television images showed several parked cars ablaze in front of a local state authority’s offices.

The area was quickly evacuated, for fear of further explosions and to allow ambulances to take away the casualties.

One person was detained in connection with the blast, said a policeman, who declined to be identified because he wasn’t authorized to speak on the matter. Hurriyet newspaper reported that two people were taken into custody, citing unidentified police officials

There have been several bomb attacks in Turkey’s main cities in recent years, many blamed on the Kurdish insurgent movement, the PKK.

However the last big attack in Ankara four years ago, which killed nine and injured 120, was blamed by police investigators on a lone, leftist suicide bomber.

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