Suspected gang members in Mexico have confessed to killing more than 40 missing students and burning their remains, Mexico's chief prosecutor has said.

Three Guerreros Unidos gang members confessed to killing the male students after police handed them over between Iguala and the neighbouring town of Cocula, Attorney General Jesus Murillo Karam said on Friday, showing videos of the taped confessions.

As long as there is no proof, our sons are alive. Felipe de la Cruz, Father of one of the missing students

The bodies were set on fire down a hill from a Cocula garbage dump with gasoline, tires, firewood and plastic, in a 14-hour-long inferno, he said.

"I know the enormous pain the information we've obtained causes the family members, a pain we all share,'' Karam said at a news conference.

"The statements and information that we have gotten unfortunately points to the murder of a large number of people in the municipality of Cocula.''

He said authorities would continue to consider the students as missing until DNA tests confirm the identities. But the chief prosecutor added that there was "a lot of evidence... that could indicate it was them."

Al Jazeera's Rachel Levin, reporting from Mexico City, said the remains have been sent to Austria for forensic examination.

"This case has gripped not only Mexico, but also the international community," she said. "Once again, it highlights the violence that Mexicans live with day in and day out."

"Families insist on getting independent verification of the DNA as they don't trust the state authorities. These children were kidnapped by police forces," Levin added.

If the confessions are proven true, the mass murder would rank among the worst massacres in a drug war that has killed more than 80,000 people, and left 22,000 others missing since 2006.

Parents want proof

Facing angry protests in the biggest crisis of his administration, President Enrique Pena Nieto vowed to hunt down all those responsible for the "horrible crime".

But the parents said they would not accept that their children are dead until they get a final ruling from independent Argentine forensic experts who are taking part in the investigation.

"As long as there is no proof, our sons are alive," Felipe de la Cruz, a spokesman for the families, said at a news conference from the missing young men's teacher-training college near Chilpancingo.

About 74 people have been detained so far in a case that prosecutors have said started when police attacked student protesters on September 26 in the city of Iguala, killing six people and taking away 43 students.

Authorities said Iguala's mayor sent police to intercept the students, who came to town to collect money. Prosecutors said the police handed the 43 students over to a drug gang.

Mayor Iguala Mayor Jose Luis Abarca and his wife, Maria de los Angeles Pineda, were detained in a Mexico City district on Tuesday after more than a month on the run.

Relatives of many of the missing students have been camped at their school, the Rural Normal School of Ayotzinapa, since the days immediately following their disappearance from Iguala.