More than 70 Chilean miners striking over unpaid wages have blocked themselves inside a shaft deep underground and are refusing food and water in protest, their union says.

"They blocked off all the entrances. They demolished them, which is preventing anyone from reaching them," Luis Chandia, union chief at the Santa Ana coal mine, said.

"They have no means of communication and said they didn't want food or water,"  

It is the second mining strike in recent months in Chile, the country in which 33 miners were famously trapped below ground -- but survived -- in an accident that captured the world's imagination in 2010.

Earlier this month, copper miners ended a strike in which they had blocked roads to mines to demand higher wages. One worker was killed by police in the 23-day protest.

The currently striking miners, who have been protesting for two weeks, are at a depth of 900 meters (3,000 feet), he said.

A total of 73 miners went on strike on August 11, initially burrowing down 650 meters, to demand their wages, which they say have gone unpaid since June.

Chandia said Monday they then upped the ante by descending to 900 meters, where he worried they could face health problems and oxygen shortages.

The blockaded coal miners have vowed to stay underground until their wages are paid.

The mine is located in Curanilahue in central Chile, some 600 kilometers south of the capital Santiago. It employs more than 170 people.

The mine is operated by a consortium owned by two local businessmen, Rodrigo Danus and Paul Fontaine, but they say they have sold it and are not responsible for the dispute.

The government has provided financial support to the miners' families and brought legal proceedings on their behalf.

"The government cannot replace people's wages or their employers' obligations," Labor Minister Ximena Rincon told radio station Cooperativa.

"The owners of the Santa Ana mine need to show their faces and answer for what they've done to these families that don't have food to eat."