Shenzhen's green GDP index increased by 3.33 percent in the past six months, officials with the municipal statistics bureau said at a press conference Friday.

"The index reaches 108.18 percent in the first half. It's a satisfactory result," said Tang Jie, secretary-general of the municipal government.

Statistics also showed that the output per square kilometer had reached 131 million yuan (US$16.38 million) this year, an increase of 13.5 percent compared with the same period last year.

The index measures the output from the high-tech, finance, logistics and cultural industries against pollution and consumption of resources.

However, the level of air pollution in Shenzhen increased slightly by 0.32 percent, which was blamed on emissions from some 1 million vehicles in Shenzhen.

Tang said the municipal government will strengthen the inspection of vehicle emissions and those failing to meet the standard will be taken off the roads.

However, the city's GDP growth is slower than the provincial average for the first time during the past decades.

"It's a positive result when considering Shenzhen is switching from extensive to intensive economic growth," said Li Hongzhong, secretary of the Shenzhen Municipal Committee of the CPC. "We will not compare the economy scale with other cities. Shenzhen will maintain its annual GDP growth at 13 percent in the coming years," Li said.

The green GDP index includes 20 assessment criteria, nine related to economic benefits, four to social benefits, four to the environment and the last three to residents' living standards.

"The green GDP index enables the municipal government to have a clear idea about what is happening in the society, the environment and the people besides a GDP number," said Deng Ping, director of the statistics bureau.