Households in rural China have seen incomes increase on average over the past three years, but the wealth gap in the vast countryside has almost reached a warning level, a top Chinese institute for rural studies said on August 21.

The cash income of rural households grew 14.13 percent from a year earlier to an average of 38,894.4 yuan ($6,123) last year, and the per-capita cash income in rural areas rose 11.95 percent to 9,260.6 yuan ($1,458), according to a survey by Central China Normal University's Center for China Rural Studies.

The survey was launched in 2009 and covered more than 6,000 rural households across the country. The figures have not been adjusted to reflect inflation.

The institute said in a report released on August 21 that the income growth was fueled by rising wages among farmers who have abandoned rural life to work as migrant laborers outside of their hometowns, mostly in cities.

Wages paid to the migrant laborers accounted for 65.7 percent of the total income of rural households, it said.

The Gini coefficient, an index reflecting the rich-poor gap, in rural China stood at 0.3949 last year, nearing the warning level of 0.4 set by the United Nations, the institute said.