The energy efficiency of China's fuel-guzzling economy is improving but the country ¡ª the world's No. 2 oil consumer ¡ª is still struggling to meet self-imposed conservation targets, the government said Tuesday.

China launched a five-year campaign in 2006 to cut energy use per unit of economic output 20 percent by 2010 amid worries about pollution and rising dependence on imported oil.

Total energy consumption per unit of economic output fell 2.78 percent in the first half of the year from the year-earlier period, the Xinhua News Agency said, citing a government report. But it said electric power used per unit of output rose 3.64 percent.

Chinese industries use 20 to 100 percent more energy per unit of output than their U.S., Japanese and other counterparts, according to the World Bank. China's government says the gap is even bigger, putting energy use at 3.4 times the world average.

Improving efficiency is a key part of efforts to reduce the ecological cost of China's 28-year-old boom, which has left it with some of the world's most polluted air and water supplies.

Last year, energy consumption per unit of output fell just 1.33 percent, far short of the 4 percent annual target.

Total energy use is soaring ¡ª despite the improved efficiency ¡ª in a boom that saw China's economy grow by 11.9 percent last quarter, its fastest quarterly rate since 1995.

Oil imports, for example, rose 11.2 percent in the first half of the year.

Some industries reported big gains in efficiency, the statistics bureau said. Its report was prepared with two cabinet bodies, the National Development and Reform Commission and the Office of the National Energy Leading Group.

Energy consumption per unit of output fell 7.76 percent in the coal industry over the year-earlier period, the report said. Construction materials producers showed a 7.84 percent gain and chemical companies a 5.17 percent improvement.

Improvements in some areas were smaller than the national average ¡ª 2.57 percent for electric power utilities and just 1.27 percent for oil and petrochemical companies.

The government is pressing local utilities to shut down older power plants and factories to install more efficient technology.