Jakarta - Indonesian police wrongly used tear gas inside a stadium to disperse rioting football fans, an internal oversight official said on Tuesday, as the country awaits answers on how a soccer match descended into chaos, killing 125 people.

In one of the world's worst stadium disasters, hundreds of spectators were crushed as they tried to flee the overpacked stadium in Malang, East Java on Saturday, after police fired tear gas to disperse agitated fans of the losing home team, Arema FC, who had poured onto the pitch.

There were no orders to use tear gas on the crowd, said Albertus Wahyurudhanto, an official with the National Police Commission, an oversight body that reports to the country's president.

"Tear gas was supposed to be (fired) outside...There are suspicions of a violation of instructions," he told reporters, adding the Commission will share its findings with a fact-finding team set up by the government.

Fans of the winning team, Persebaya Surabaya, had been banned from attending the game for fear of clashes, so most of the victims, which included 33 minors, were the home club Arema's fans.

While the stadium in Malang has several exit gates, spectators told Reuters some of these were locked during Saturday's match, causing bottlenecks as stampeding fans tried to flee. Medics said some victims died of suffocation, while others suffered head injuries.

Haura, a 20-year-old spectator and university student, said the incident was "so terrifying. I felt suffocated and my eyes hurt."

Wahyurudhanto said it was unclear why some exits had been locked.

Hooliganism, heavy-handed policing and event mismanagement are not unusual in Indonesia, where football is hugely popular and sparks fierce rivalries between fans of various clubs.

Football's world governing body FIFA bans the use of "crowd control gas" and weapons at matches.

Choirul Aman on Indonesia's human rights body, Komnas HAM, said on Monday that if tear gas hadn't been fired "maybe there wouldn't have been chaos."

Dozens of police officers have been placed under investigation and at least nine have been suspended, a police spokesperson said on Monday.

(Editing by Kanupriya Kapoor)