According to studies of satellite images from 2009, nearly 20,000 hectares of arable land was illegally used to build roads and railways. The 20,000 hectares comprised about 57 percent of the total mass of illegally used arable land that year.

"The satellite images show that the illegal use of land for road and railway construction is a serious problem," Yun said, adding that the situation in 2010 is not likely to be any better.

He said some local authorities ignore the process they are supposed to follow to apply for land through local land bureaus.

The Ministry of Land and Resources, the Ministry of Railways and the Ministry of Transport jointly released a notice on March 7 calling for the strengthening and improvement of the supervision of road and railway projects.

According to the notice, strict assessments will be made before land is approved for use in road and rail projects.

Feng Zhenglin, vice-minister of transport, said at the conference that demand for land for road projects will climb, but the ministry will take measures to save space and reduce the loss of arable land.

Lu Dongfu, vice-minister of railways, said reducing the use of arable land will also be a standard for future railway projects.

China's land watchdog is facing a severe challenge during the coming five years to protect the country's shrinking arable land reserves because booming railway and highway construction is called for in the 12th Five-Year Plan (2011-2015).

The plan says the length of railway lines will reach 45,000 kilometers while roads will extend for 83,000 kilometers by the end of 2015.

"The fast development expected during the coming five years will put us under great pressure," Yun said.