Volkswacht Bodensee - Mexican president vows justice after army kills six migrants

The killings "must be investigated and punished," Sheinbaum said, adding that the victims were from Egypt, El Salvador and Peru.

The state prosecutor's office would investigate the incident late Tuesday in southern Chiapas state, including whether commanders were also responsible, she told a news conference.

"A situation like this cannot be repeated," she added.

The shooting happened on the same day that Sheinbaum was sworn in as president with a vow to respect human rights and avoid repression by security forces.

According to the defense ministry, a military patrol saw a vehicle -- followed by two flatbed trucks like those used by criminals -- traveling at high speed and apparently attempting to flee.

"Military personnel reported hearing gunshots, so two soldiers activated their weapons, stopping one of the flatbed trucks," the statement said.

The patrol found 33 migrants from countries including Egypt, Nepal, Cuba, India and Pakistan.

Four of the migrants died at the scene while two of the 12 injured lost their lives at the hospital, it said.

Thousands of migrants from many countries travel through Mexico each year in buses, overcrowded trailers and on freight trains in an attempt to reach the US-Mexican border.

They run the risk of fatal accidents, kidnapping by criminal groups and extortion by corrupt officials.

T.Egger--VB