BEIJING, July 13 (Reuters) - Hundreds of farmers in southwest China protested against a gas leak that damaged crops, a human rights group said on Friday, at a time when the government is seeking to ease public anger over environmental threats.

Farmers near Mount Emei in Sichuan province blocked a highway to protest against an aluminium company they said was responsible for the leak that contaminated grapes and other crops, the Hong Kong-based Information Center for Human Rights and Democracy said in a fax.

The Center, which often reports on protests in China, said the spill happened on June 24 and farmers began blocking the highway from July 10 to demand a total of 8 million yuan ($1.1 million) in compensation.

Ten residents were injured on Thursday when policed cleared the road, and five people were detained, the report said.

Villagers and officials could not be contacted to confirm the report. The Center said Emei officials verified the incident but said it was up to environmental authorities to determine whether the gas leak was a threat to people's health.

Beset by growing public alarm about spoiled land, air and water, China has promised to cut major pollutants by 10 percent between 2006 and 2010. But last year the country failed to meet the annual target.

On Wednesday, Chinese Premier Wen Jiabao chaired a meeting that warned efforts to meet the pollution target still faced "big difficulties," the official Xinhua news agency reported.

Chief of the State Environmental Protection Administration (SEPA), Zhou Shengxian, said last week that public discontent with pollution "has resulted in a rising number of 'mass incidents'" -- an official euphemism for riots, protests and collective petitions.

Zhou did not give overall numbers for such acts but said SEPA had received 1,814 citizen petitions in the first five months of this year demanding an improved environment, an 8 percent rise on the same period of 2006, Xinhua reported.

He lambasted local officials, eager to generate revenue and jobs, who have fended off pollution controls on local businesses.