Authorities will plant 18 million trees in Mexico City and its surrounding suburbs as part of efforts to combat air pollution, the government said.

Environment Minister Rafael Pacchiano on Monday dubbed it a "historic reforestation" to reinforce the "green belt in the megalopolis."

The greater Mexico City area was hit by the worst air pollution in more than a decade in March, prompting authorities to restrict traffic for the 5.4 million vehicles that circulate daily.

Pacchiano said that the lack of wind and record high temperatures in March contributed to an increase in ozone levels.

Other new measures announced by Pacchiano include replacing 1,000 taxis that are more than 10 years old with hybrid cars and stepping up a program to renew cargo and passenger transport vehicles.

Anti-pollution rules will also be tightened in industry.

The government imposed temporary car restrictions between April and June 30, forcing all vehicles to stay home at least once a week. Normally, older vehicles and those that fail emissions tests have traffic restrictions.

Last month, the environment ministry unveiled new rules to prevent corruption at emission inspection centers that have allowed polluting cars to remain on the road.