The situation is very tense

Police official

Hundreds of local farm workers, students and teachers have blocked access roads and the only railway line, barring the way to tourists, who have been reduced to taking pictures of the demonstrators rather than the ruins themselves.

The protesters want the government to invest more money in the area, and especially to improve the dirt roads.

A police official from Quillabamba, some 61km (38 miles) from Machu Picchu, said: "The situation is very tense here - the whole region has been paralysed for four days.

"All access roads are blocked."

On Wednesday protesters blocked the railway line that ferries hundreds of tourists up to Machu Picchu daily, 2,400 metres (7,782 feet) high in the Andes.

President Alberto Fujimori has made regional decentralisation a key theme of his new government, and has recently adopted measures to boost the agriculture sector.

The protest came just days after a centuries-old sundial at Machu Picchu was damaged in a shoot for a beer commercial.