ACAPULCO (AFP) - Mexican soldiers will from Tuesday start guarding elementary and other schools in the resort town of Acapulco that have been closed since November because of gangs threatening teachers, officials said.

Some 1,000 soldiers will take up positions outside 107 kindergartens, elementary, secondary and other schools in high-crime areas of the city, said Alfredo Miranda, the city's education chief.

More than 31,000 students have been unable to attend classes since November, when teachers went on strike complaining that they were being threatened by crime gangs.

Three teachers were kidnapped, and others were forced to pay parts of their salaries to the crime gangs through extortion, teachers said.

Now, areas surrounding schools will be guarded by police and soldiers, said a statement from the education department of Guerrero state, where 43 students at a teachers college were murdered in September, sparking widespread protests.

Since December the federal government has taken charge of security in Acapulco, which has been torn by clashes among rival drug gangs and has become one of the country's most violent regions.

The port city has also been shaken by repeated protests over the massacre of the 43 students the town of Iguala, which is 220km from Acapulco.