Mexico President Enrique Pena Nieto denounced Saturday the violence at protests over 43 young men who are missing and feared to have been massacred.
Speaking on his return from a six-day trip to China and Australia for the APEC and G20 summits, Pena Nieto also defended himself against suggestions he should not have traveled abroad amid the fury and shock over the case.
The Mexican leader stressed that "two out of every three dollars of wealth" in Mexico depends on foreign trade, so his presence at international events was essential.
But he said that, while abroad, he remained "very attentive" to the events back home, which have constituted the biggest crisis to hit his administration since he took office in December 2012.
He also stressed that, although he "understands the pain" the case has caused, "I'm also very clear that this is no way can be a call to violence."
Protests have rocked a number of Mexican cities this week, with the Guerrero state congress set ablaze on Tuesday in the escalating demonstrations.
Pena Nieto said his administration would take every opportunity for dialogue with the protesters, saying any use of force to subdue them would be a "last resort."
However, he noted "the state legitimately has the power to make use of it when other mechanisms to restore order have been exhausted."
The 43 trainee teachers vanished on September 26.
Authorities say the students were abducted in Iguala, in Guerrero state, by police and handed over to a drug cartel before being murdered and set alight -- a claim contested by the victims' families, who hold out hope they were abducted but not killed.
Activists say the students were attacked by police and abducted amid fears they planned to disrupt a speech given by the wife of local mayor Jose Luis Abarca, who was arrested on November 4.
The case has outraged Mexicans accustomed to horrific violence witnessed since former president Felipe Calderon launched a crackdown on drug gangs in 2006.