Governor of Mexican state where 43 students disappeared quits

The governor of a Mexican state roiled by the disappearance of dozens of students that has sparked protests and embarrassed President Enrique Pena Nieto, bowed to pressure on Thursday and said he was standing down.

Angel Aguirre, governor of the impoverished state of Guerrero in southwest Mexico, said he was taking a leave of absence. The move is the only option open to him given he cannot resign by law. His replacement will be chosen by the Guerrero state assembly.

Aguirre, 58, a member of the leftist Party of the Democratic Revolution (PRD), has faced sustained criticism since the disappearance of 43 students in the city of Iguala after clashes with police there the night of Sept. 26.

Police suspected of being in league with local gangsters shot dead one of the students that night and abducted at least two dozen more, according to Mexico's attorney general.

A gaunt-looking Aguirre said he was standing down to help improve the political climate around the investigation.

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"Let it be clear that Angel Aguirre, even though he's no longer in the job, will be ready to contribute to investigations to clear up the facts," PRD leader Carlos Navarrete said.

Dozens of bodies have been uncovered in mass graves in the hills around Iguala, whose mayor, accused with his wife and police chief of orchestrating the students' disappearance, is on the run. However, investigators say they have yet to identify the remains of any of the students.

The incident, which has shocked the country and sparked protest marches across Mexico, was the latest in a string of killings and discoveries of mass graves in recent months.

Ruling party politician Gilberto Sanchez, a former Mexico City lawmaker who is standing in for federal Congressman Manuel Anorve, was shot dead outside his home in Mexico City late on Wednesday.

Two other politicians have been murdered since September, one of whom was kidnapped in broad daylight from his vehicle on a busy highway.

Lawmakers fear the security lapses will undermine Pena Nieto's reforms aimed at bringing in investment to revive the economy, which has been the main focus of his government.

Critics say Pena Nieto's economic reforms have come at the expense of a strategy to stop gang violence that has claimed around 100,000 lives since the start of 2007.

Aguirre, who once belonged to Pena Nieto's Institutional Revolutionary Party (PRI), also served as governor of Guerrero for the PRI from 1996 to 1999 after the then-incumbent stepped down following a massacre of 17 farmers by state police.

Over the past two years, government buildings and political offices in Guerrero have been trashed, occupied and set fire to by critics of the administration of Aguirre, who had cut an increasingly isolated figure within the PRD in recent weeks.

(Additional reporting by Gabriel Stargardter and Michael O'Boyle; Editing by Simon Gardner, Diane Craft and Cynthia Osterman)