MEXICO CITY (AFP) - Mexican police on Tuesday detained a fugitive former mayor and his wife accused of ordering a deadly police attack that left 43 students missing, raising hopes of a break in a case bedeviling the nation.

Jose Luis Abarca, the former mayor of the southern city of Iguala, and Maria de los Angeles Pineda were captured by federal officers before dawn in Mexico City's populous working-class district of Iztapalapa, authorities said.

Officials hope the arrest will yield new clues about the whereabouts of the students in a disappearance that has drawn international condemnation, sparked national protests and shaken President Enrique Pena Nieto's administration.

"I hope that this arrest will contribute in a decisive manner... to the investigation undertaken by the attorney-general's office," said Pena Nieto, who last week met parents angry at the pace of the probe.

The couple were arrested in a small, cement-coloured house with a dusty courtyard, far from their opulent life in Iguala, where Abarca owned jewellery stores and his wife allegedly ran local operations for the Guerreros Unidos drug gang.

"There was no violence in the operation," a national security commission spokesman told AFP on condition of anonymity, adding that the two were being interrogated by federal prosecutors.

A neighbour said the house used to be owned by an elderly couple who died months ago. Others saw a woman go in and out periodically.

"We were very scared" when the police descended on the house, a woman living nearby told AFP.

Authorities say the students vanished on Sept 26 after municipal police shot at their buses in the city of Iguala, 200km south of Mexico City, and then handed the 43 to the Guerreros Unidos.

Six people died in the night of violence.

In one gangland-style killing, a dead student was found with his facial skin peeled off and eyes gouged out.

The teacher college students remain missing despite a vast search operation by troops, helicopters and boats in the state of Guerrero, where a dozen mass graves containing 38 unidentified bodies have been discovered.

Guerrero's interim governor, Rogelio Ortego, told the Televisa network that the capture could lead to "substantial leads" in the search.

Manuel Martinez, a spokesman for the families of the missing, told AFP that investigators "must make him speak" because Abarca "knows where they are."

Abarca, his wife, and the city's police chief went on the run two days after the Sept 26 police attack.

The Guerrero state legislature impeached him weeks later.

Authorities say Abarca ordered the officers to confront the students over fears that they would derail a speech by his wife, who was the head of the town's child protection agency.

Fellow students from the left-wing college near the Guerrero capital Chilpancingo said they went to Iguala to raise funds but acknowledged they had seized the buses to transport themselves.

Dubbed the "imperial couple," the mayor and his wife have since been linked to the Guerreros Unidos. Pineda also has three brothers who are known members of the Beltran Leyva drug cartel.

Abarca's family says he is innocent.

Abarca was elected in 2012 and remained in power despite accusations by members of his own leftist Democratic Revolution Party that he murdered a farm activist last year.

Prosecutors have said they never had enough evidence to charge him for the murder. Abarca denied killing the man.

Authorities say Pineda aspired to become mayor while running local operations for the Guerreros Unidos.

The mass disappearance has overshadowed Pena Nieto's attempts to steer Mexico's narrative away from the drug war and toward economic reforms that have drawn international praise.

Families of the missing have voiced frustration over the lack of progress in the search and expressed their anger to Pena Nieto in a private meeting last week.

Authorities have detained 56 people, including 22 Iguala police officers and 14 members of the municipal force in the neighboring town of Cocula.

Guerreros Unidos leader Sidronio Casarrubias was caught last month.

Guerrero's embattled governor, Angel Aguirre, has resigned over the case.

Suspects have led investigators to several mass graves, but DNA tests have shown so far that the students are not among the remains.

Mexicans have held a series of protests over the disappearance. Some have turned violent, with demonstrators torching part of the Guerrero government headquarters last month.