Mexico's President Enrique Pena Nieto addresses an audience in Mexico City November 27, 2014. [Photo/Agencies]

MEXICO CITY - Embattled President Enrique Pena Nieto on Thursday vowed to simplify Mexico's chaotic police structure and stop collusion between officials and drug gangs as he tried to defuse anger over the apparent massacre of 43 students in September.

Pena Nieto is under growing pressure from protesters to end impunity and brutality by security forces since the trainee teachers were abducted by corrupt police and handed over to a local drug gang in the southwestern city of Iguala on Sept. 26.

The government says the students were almost certainly murdered and their bodies incinerated, but it is still investigating the case that has sparked the biggest crisis of Pena Nieto's two-year rule.

"Mexico cannot continue like this," Pena Nieto said in a speech to an assembly of Mexico's political leaders.

It was his most concerted effort to retake the initiative on an issue that has left his government scrambling for answers.

"After Iguala, Mexico has to change," he added, speaking inside the ceremonial presidential palace in Mexico City whose door was set ablaze by demonstrators earlier this month. "Our country has been shaken by cruelty and barbarism."

Promising a new law to stop the infiltration of local governments by organized crime, Pena Nieto also pledged to reform the penal system and send an proposal to Congress to unify multi-layered police forces in Mexico's 31 states.

Mexico has a plethora of police forces, as hundreds of municipalities, the states and the capital Mexico City each have their own. But poor training and salaries as low as 5,000 pesos ($370) per month encourage corruption.

Several of Pena Nieto's predecessors also undertook police reforms, but corruption persists and infiltration by gangs is widespread. Some Mexican states which dismantled municipal forces remain wracked by violent crime.

Alejandro Hope, an independent security consultant who used to work for Mexican state intelligence, noted that a 2009 bid to create a unified police command structure "failed completely" and was skeptical the new plan would reassure the populace.

"There was very little on the subject of justice," he said.

Only about 2 percent of crimes in Mexico result in convictions. Despite the indictments of several senior Mexican officials in U.S. courts, very few of them have had to face investigations, let alone trial, at home.

The murder rate has fallen somewhat since Pena Nieto took office two years ago, but public confidence in his ability to guarantee law and order has been shattered since the atrocities in Iguala.

Six people, including three other trainee teachers, were also killed that September night when the 43 were abducted.

Since then, Pena Nieto has yet to visit Iguala or the students' training college in the nearby town of Ayotzinapa, though he attempted to express his solidarity with the public outrage in the speech.

"The shout of 'We are all Ayotzinapa' is a call to continue transforming Mexico," the president said.

The government will launch a special security operation in Mexico's troubled southwest, he said, adding that it will be backed by plans to boost growth in three impoverished areas in the south and west of the country.

He admitted that the gap between rich and poor in Mexico was only getting worse.

"Today there are two Mexicos: One that is part of the global economy with growing levels of income, development and well-being; and then there is a poorer Mexico with historical problems that have been unresolved for generations."