Malang, Indonesia - Hundreds of Indonesians paid tribute Sunday to the victims of a football stadium crush a year ago that killed 135 people in one of the world's worst sports disasters, while some locals entered the ground and started fires on the pitch.

Grieving relatives, survivors and fans gathered for a mass prayer at the Kanjuruhan stadium in the East Javan city of Malang, where the fatal stampede unfolded at the end of a match between Arema FC and fierce rivals Persebaya Surabaya.

Locals entered the stadium through its open gates in the evening after Sunday's prayers, starting fires on the pitch and chanting Arema songs, according to an AFP journalist.

No police were present, but at least one fire engine arrived to douse the fires as people started to leave the stadium.

One year ago, police fired tear gas into packed stands when home supporters invaded the pitch, sparking a rush to the stadium's small exits, some of which were closed. Forty-three children were among the dead and hundreds more people were injured in the crush.

Some relatives of the victims broke down in tears on Sunday and others fainted as they prayed at the makeshift memorial at the stadium's Gate 13, where many of the victims died.

'I felt very painful, but we all prayed together. ... Hopefully all of the dead spirits are in heaven,' Misiati, who like many Indonesians goes by one name, told AFP.

Her 20-year-old son, Fillah Aziz Firmansyah, was among those killed.

'Please investigate thoroughly. Don't play with the laws,' she said.

Some relatives are still seeking justice, claiming prison sentences of between one and two-and-a-half years handed to three police officers and two civilians for negligence causing death were too lenient.

FIFA, football's world governing body, bans the use of tear gas in stadiums.

Wahyu Jarwati, 51, whose child's friend was also one of the victims, prayed and expressed sadness that so many children were killed.

'Everyone was innocent as they only wanted to watch their team. But in reality, they went home only in their name,' she said.

President Joko Widodo ordered a nationwide stadium audit after the tragedy and pledged to demolish and rebuild Kanjuruhan, but it remains standing.

Several victims' relatives earlier read a statement before the prayer service, listing demands including a fair trial for those responsible and calling on Widodo to suspend the stadium's planned renovation so a reconstruction of events could take place.

They also demanded Indonesia's football association declare October 1 a national day of mourning.