Protesters angry at the alleged massacre of 43 Mexican students have clashed with police and besieged Acapulco's airport.
Thousands of people marched to the Pacific resort town's international airport on Monday, with parents of the students leading the demonstration along with comrades from the missing young men's teacher-training college in the southern state of Guerrero.
The rally followed violent protests that erupted over the weekend after authorities said gang hitmen confessed to murdering the 43 students and incinerating their bodies in September after corrupt local police handed the men over.
In a case causing national revulsion, Attorney-General Jesus Murillo Karam downplayed chances of ever identifying the charred remains, warning that only two bones were salvageable for DNA tests.
"Pena out! Pena murderer! Stay in China," protesters chanted, referring to President Enrique Pena Nieto's controversial decision to travel to a summit in Beijing amid public fury over the crime.
The protesters blocked the airport's entrance for more than three hours, with some masked men armed with sticks, though several tourists snuck in through a private terminal.
Before reaching the airport, protesters threw stones and a firebomb at riot police who were blocking their way, injuring at least 20 officers, a security official said.
Tourists had to reach the airport by foot, pulling their suitcases behind them. Three flights were cancelled.
"Every Mexican is in this struggle," said Beatriz Barros, a Mexican traveller.
"I don't care if I arrive home later because what they (the protesters) are doing is fair."
Authorities say gang-linked police shot at busloads of students in the Guerrero city of Iguala on September 26, in a night of violence that left six people dead.
The police then handed the 43 abducted students to the Guerreros Unidos drug gang, prosecutors say.
Authorities say Iguala's mayor ordered police to confront the students over fears they would interrupt a speech by his wife, who aspired to succeed him.
The students had travelled to Iguala to raise funds but hijacked four buses to return home, a common practice among the young men from the college known for its radical left-wing politics.
Officials stopped short of declaring the students dead, stressing they were waiting for DNA results.
The government has asked experts from Austria's University of Innsbruck to identify the remains.
Parents of the missing students, who deeply distrust the government, say they will only believe their sons are dead once they get independent DNA test results.
"We want the government to do everything possible as soon as possible to find the boys alive, because they are deceiving us," said Carlos Ivan, father of one of the missing students.
