Mexico City (AFP) - The United Nations in Mexico urged authorities to conduct an "effective" search for 43 students who vanished after a deadly police shooting last week, calling it "one of the most terrible events of recent times."
The UN intervention came as relatives of the aspiring teachers criticized search efforts and met with interior ministry officials, pleading for a "serious" federal investigation to find the students in the gang-plagued southern state of Guerrero.
Witnesses told AFP that municipal police officers hauled away the students in patrol cars after shooting at buses that the youngsters had hijacked in the town of Iguala on September 26.
Three students were killed in the shooting. Three other people died in a gun attack on a soccer team bus on the outskirts of town. Authorities have detained 22 officers over the shootings.
"The extreme gravity of the incidents linked to the disappearance of so many people make it one of the most terrible events of recent times," the UN said.
It called on the government to coordinate and reinforce "all measures at its disposal to conduct an effective and diligent search."
The UN urged the abductors to return the students alive and called on the government to take measures to ensure that violations of human rights "like those that were reported are not repeated."
The UN's human rights body has dispatched personnel to the region and has contacted victims, families and local authorities.
The police shooting in Iguala came as Mexico's army faces its own abuse allegations after three soldiers were charged with homicide over the June killing of 22 drug suspects south of the capital.
In the Iguala case, state prosecutors issued arrest warrants for Mayor Jose Luis Albarca and the police chief, who have disappeared from public view.
"One hypothesis that we have is that the mayor thought that the comrades were going to boycott or interrupt a speech his wife was going to give that afternoon and his state-of-the-town speech the next day," said Vidulfo Rosales, a human rights lawyer representing the families of the missing.
The students, from a teacher training college near the state capital Chilpancingo, say they had gone to Iguala for fundraising activities and had taken buses to return home when they were attacked.
- 'It's a farce' -
Forcing bus drivers to transport them is a common practice among the region's student-teachers.
After a meeting between relatives and Deputy Interior Minister Luis Enrique Miranda in Mexico City, Rosales said the official pledged that federal authorities would draw up a new search strategy.
"We believe that there's no serious, exhaustive, objective, responsible search preceded by a serious strategy that ensures success," Rosales said.
Relatives voiced concerns that municipal police officers handed the students to a violent drug gang. A gang is suspected in participating in the second shooting.
Scores of soldiers accompanied nine relatives who went door to door on Wednesday around Iguala, handing out pictures of the missing and asking for any information.
But relatives later complained that the search lacked any prior investigations by the authorities.
Then on Thursday, Governor Angel Aguirre deployed 1,600 government employees to Iguala, drawing scorn from relatives who say state workers are not suited for such work.
"It's a farce, a mockery," said Anaceli, a 26-year-old law student who refused to give her last name and whose 18-year-old nephew is missing.
"We are not happy," said Meliton Ortega, who is looking for his 17-year-old nephew. "We will be happy when our boys reappear."