In a testament to just how deep tensions are running, Buddhist fishermen and Muslim asylum seekers who fled Myanmar hoping for a better life brawled with rocks and knives on Friday at an immigration detention centre in Indonesia, leaving eight dead and another 15 injured, police said.

The deadly melee broke out in North Sumatra province, where more than 100 Rohingya migrants most intercepted off Indonesia’s coast in rickety boats and 11 illegal fishermen from Myanmar were being held together, said local police chief Endro Kiswanto.

Insults were quickly traded, and the cleric was allegedly stabbed by a fisherman, said Yusuf Umardani, detention centre chief. When the cleric screamed, his friends jumped in to help. From there, a burst of fighting broke out so quickly, security guards were too late to stop it.

“The violence took place so fast, and it was completely unexpected because they had been living peacefully here so far,” Mr. Umardani said. “Most of the dead victims suffered severe head injuries. Apparently, they fought using anything that they could get rocks, wood, chairs and knives.”

Eight Buddhists were killed, and 15 Rohingya were injured. Three other Buddhists escaped unharmed, Mr. Kiswanto said.

“I was out with two of my friends, and when we came back ... we saw them,” Win Thike Oo, one of the fishermen who survived, told an Associated Press photographer at the scene. “Our friends were covered in blood. If we were there at the time, we would also be dead.”

All of the victims were rushed to a hospital in the provincial capital, Medan, about 23 kilometres (14 miles) south of Belawan. The three surviving fishermen have been moved to a separate building and hundreds of police have been deployed to secure the centre. A forensics team was working to collect evidence, and determine how the migrants obtained knives.

Mr. Kiswanto said 25 Rohingya asylum seekers were being questioned by police and would be prosecuted under Indonesia law if suspected of being involved in the killings. Police are also reviewing surveillance recordings of the incident.

Last year, hundreds of people were killed and more than 100,000 left homeless in violence in western Myanmar between ethnic Rakhine Buddhists and Rohingya Muslims.

“We actually don’t understand about what is happening in my country,” said survivor Oo, who has been detained for nine months at the centre. “We are only fishermen. We don’t care about politics or conflict.”