Protesting teachers and their supporters once again blocked at least half a dozen highways in southern Mexico, hours after the government demanded an end to the highway blockades.

The federal police reported that blockades had been re-installed Saturday on roads in the southern states of Oaxaca and Chiapas.

Interior Secretary Miguel Angel Osorio Chong said late Friday the blockades had hurt millions and "must end," adding "time is up."

Teachers protesting mandatory evaluations had loosened the highway blockades to allow gasoline tanker trucks through. But food and other basic necessities were in short supply.

The governmental National Human Rights Commission later issued a call "to all parties involved to re-establish dialogue, in an atmosphere of responsibility, civility and respect for peoples' dignity."