Mexico beefs up security.

Mexico's government has moved about 40,000 federal police, soldiers and marines into several restive southern states to try to safeguard Sunday's midterm elections, a source close to the operation said on Saturday.

The force will be spread among Oaxaca, Chiapas, Guerrero and Michoacan states, where a union and other radical groups have vowed to disrupt the vote.

A splinter teachers union as well as other activist groups have in recent days sowed chaos in the states, burning ballots and attacking the offices of local political parties, among other disruptions.

National Security Commissioner Monte Alejandro Rubido told reporters on Saturday the operation to dispatch federal police and soldiers to the trouble spots ahead of the election began on Friday.

The lower house of Mexico's Congress, nine state governorships and more than 1,000 posts in state legislatures and mayors' offices are up for grabs in Sunday's election.