Chile closed its main border crossing with Peru after torrential rains on Monday washed anti-personnel and anti-tank mines onto a key highway, authorities said.

"The mines came down toward the northern Route 5, and with the carabineros (police) and the army, a decision was taken to close the highway," said Ximena Valcarce, mayor of Arica. "Nobody is getting through," she said.

Valcarce did not say how many mines were dislodged during the rains but she said police bomb disposal experts had detonated four explosive devices found on the highway.

Route 5 is heavily traveled by tourists, traders and Peruvians who work in the northern Chilean city of Arica, 2,100 kilometers (1,300 miles) north of Santiago.

Border tensions periodically flare as a legacy of a mid-19th century war that ended with the transfer to Chile of a portion of southern Peru and Bolivia's entire Pacific coastline.

The Chilean military planted thousands of anti-personnel and anti-tank mines in a mountainous border area called Los Escritores in 1975, when the country was ruled by general Augusto Pinochet.

Chile has been working to de-mine the area since 2004 under an international treaty banning anti-personnel mines.