Mexican marines guard the site where an unspecified number of bodies were found in clandestine graves. (Agence France-Presse)
Hundreds of civilian militiamen scoured a southern Mexico town on Wednesday in search of 43 missing students amid fears they were executed by a gang working with local police.
As the self-defense forces and federal police carried out the search in the town of Iguala, thousands of people protested in Guerrero state capital Chilpancingo to demand justice in a case that has shocked Mexico.
Protests were also planned in Mexico City to pressure the government of President Enrique Pena Nieto to investigate why gang-linked police attacked the students on September 26.
In Iguala, a town of 140,000 people surrounded by mountains and corn fields, the militiamen climbed a hill, using machetes to cut through vegetation near the site of a mass grave where 28 unidentified bodies were found last weekend.
"We will find the young men, dead or alive," said a self-defense commander called Moises, whose group emerged last year to combat gangs plaguing towns in the rural mountains of Guerrero.
But authorities issued an order via radio for them to turn around.
"The police only conducts searches near roads. We will cover the whole ground," said Bruno Placido, leader of the UPOEG community police movement.
Pena Nieto deployed hundreds of federal forces to take over security in Iguala on Monday as well as 30 investigators from the attorney general's office.
The United States, the United Nations and the Organization of American States, along with international human rights groups, have pressed Pena Nieto to solve the case.
Authorities say the municipal police and its Guerrero Unidos gang allies shot at buses seized by the students on the night of September 26.
Several students, from a teacher-training college where radical students often have commandeered buses, were later seen bundled into patrol cars.
Two hitmen confessed to the authorities that they killed 17 students at the same site where the mass grave was found last weekend.
But authorities say it will take at least two weeks for DNA tests to confirm the identities of the bodies.