Things are looking grim for China's auto market, as sales have slipped for four months in a row compared with the same period last year.

Vehicles sold in August stood at 1.66 million units, a 3 percent fall year-on-year, according to the Chinese Association of Automobile Manufacturers.

"We have seen monthly sales fall year-on-year from May," said Chen Shihua, director of the association's information center, at a news conference on Thursday.

Chen said the association did not anticipate sales would "fall into such a situation" when it gave its estimate at the start of the year that the Chinese market would grow at 7 percent.

The association has slashed its estimate to 3 percent yet that still seems too high a figure considering China's sluggish performance.

The association's statistics show that vehicles sold in the first eight months of the year totaled 15.01 million units, 100 or so units less than the same period a year earlier.

Despite lackluster sales, it is too early to predict if auto sales in 2015 will be lower than in 2014, said Shi Jianhua, deputy secretary-general of the association.

He said weak sales are a result of downward economic pressure in China, the turbulent stock market and potential customers' postponement of car purchases as it has been reported that China will not charge a tariff on imported cars from 2016, 15 years after its accession into the World Trade Organization.

"That is pure speculation," Shi said. "We adjusted our tariff when we joined the WTO and the level will not change in 2016."

Shi urged potential buyers to discard their wait-and-see attitude to boost the passenger vehicle market.

Monthly sales of passenger cars have been falling year-on-on since June.

A total of 1.42 million units were sold in August, an 11.4 percent rise from July but a 3.4 percent fall from a year earlier. The number of passenger cars manufactured in the month fell 9.4 percent year-on-year.

Things would have been even worse if SUV sales had not rocketed. In August, 453,200 SUVs were sold, a 45.58 percent rise year-on-year.