Furious protesters tried to break into Mexico City's National Palace during nationwide demonstrations over the deaths of 43 students that has angered the nation.

Protesters on Saturday slammed metal barricades against the door and briefly set it on fire but could not get into the palace, which is mostly used by President Enrique Pena Nieto for ceremonies.

Hundreds of demonstrators also burned several vehicles and threw firebombs at a southern Mexican state's headquarters.

More than 300 students, many wearing masks, descended on the Guerrero government headquarters on and burned around 10 vehicles, including trucks.

Mexico was confronted with one of the grisliest tragedies in years of drug violence after gang suspects confessed to slaughtering 43 missing students and dumping their charred remains in a river.

The confessions may have brought a tragic end to the mystery, but parents of the victims refuse to accept they are dead until DNA tests confirm their identities, saying the government has repeatedly told them lies.

"It appears that the federal government, with great irresponsibility, is interested in closing this matter because it's all based in testimony. There is nothing definitive," Meliton Ortega, uncle of a missing student, told AFP news agency on Saturday.

The case is the toughest challenge yet to face Pena Nieto, who took office two years ago vowing to restore order in Mexico, where about 80,000 people have died in violence linked to organised crime since 2006.

Forensic examination

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

"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 said.

Three suspected Guerreros Unidos gang members told investigators that local police handed them the students between the southern towns of Iguala and Cocula.

In taped confessions, the suspects said they bundled the 43 in the back of two trucks, took them to a nearby landfill, killed them and used fuel, wood, tyres and plastic to burn their bodies for 14 hours.

Authorities have arrested 74 people, including the ousted mayor of Iguala, Jose Luis Abarca, his wife Maria de los Angeles Pineda, 36 police officers and several Guerreros Unidos operatives.