Protesters smashed up shops and clashed with riot police in Mexico City on the second anniversary of Enrique Pena Nieto's presidency yesterday amid rising tensions over the abduction and apparent massacre of 43 trainee teachers.

Brandishing bats and fire bombs, masked protesters attacked banks and restaurants along the capital's iconic Reforma Boulevard, where thousands had gathered to demand justice for the missing students.

Scores of riot police were deployed to restore law and order to Mexico City's central business district, but authorities struggled to control the unruly crowd. A number of injuries were reported by paramedics on hand.

The disappearances of the students have been the toughest challenge yet to face Pena Nieto. After more than two months since the disappearance of the students in Iguala, Guerrero, many have blamed the president for the feared massacre.

Earlier this month Pena Nieto vowed to introduce constitutional reforms to simplify Mexico's chaotic police structure and stop collusion between officials and drug gangs as he tries to defuse anger.

But the president's promises have fallen on deaf ears with the whereabouts of the missing still unknown.

"We're going to look for them. We're going to find them because it's been more than two months and we don't know anything about our children," said father of one of the missing students, Clemente Rodriguez.

Pena Nieto took office two years ago vowing to restore order in Mexico, where about 100,000 people have died in violence linked to organized crime since 2007.

His two-year anniversary in office comes as Pena Nieto's approval rating tumbles to just 39 per cent, according to Mexico City daily Reforma. It was the lowest approval rating of a president recorded since 1996 when then President Ernesto Zedillo was struggling to contain a financial and economic crisis.