Ethnic Mongolians protested the arrest of 22 people following clashes with police over land rights in northern China's Inner Mongolia region, reports said on Thursday, according to dpa. About 40 Mongolians marched to the government headquarters in Inner Mongolia's Naiman Banner on Wednesday to demand their land rights and the release of the 22 protesters detained a day earlier, the US-based Southern Mongolian Human Rights Information Center said. "We have been here all day demanding the government release the detainees, but the government continues to ignore our grievances," the centre quoted Chenfuulong, an organizer of the protests, as saying by telephone. Like many Mongolians, he uses only one name. It said several hundred Mongolians had clashed with dozens of police on Tuesday, with at least five protesters seriously injured. A photograph posted on the information centre's website, www.smhric.org, showed more than 20 protesters standing behind a long banner bearing the message: "Illegal detention. Release the people. Return our land." The protests began after a Chinese logging firm planted trees on farmland claimed by the Mongolians. US-based Radio Free Asia quoted Li Yushan, a local official from the ruling Communist Party, as saying the protesters had refused a government offer to negotiate over the land rights. The information centre quoted a protester as saying officials had met five of the Mongolians but promised to release those detained only if the group signed an agreement to stop protesting the use of the land by the Xing Long Gao Forestry Company. The death of two Mongolians during land protests last year set off the largest protests by Mongolians in Inner Mongolia for 20 years, with thousands of people gathering in several towns and cities in late May and early June. Following the protests, Chinese leaders promised to improve the economy and environment of the vast Inner Mongolia region. But officials said the region would remain at the forefront of a national plan to expand coal production by developing large open-cast mines. Protests erupted again in October after the death of a third Mongolian land activist who had tried to block a truck from crossing grassland. About 4 million ethnic Mongolians live in China, most of them in Inner Mongolia, where they make up less than 20 per cent of the region's population of more than 20 million. Many Mongolians resent what they perceive as encroachment by the majority Han Chinese population upon the region's grazing lands.