The number of vehicles registered in Beijing picked up pace in early 2010, government figures showed Wednesday, putting the Chinese capital on course to have five million cars on the roads by year's end.

The total number of cars registered in the first four months of 2010 rose 23.8 percent from a year earlier to 248,000, the Beijing municipal taxation office, which collects auto purchasing taxes, told AFP.

That means an average 15,500 new cars hit the city's roads every week during the January-April period, in a sign of the rising affluence of the middle class -- and a sign that Beijing's notoriously bad air quality could further suffer.

If the trend continues, the number of cars in Beijing could near five million by the end of the year. The four million mark was passed in December.

That would mean that on average more than a quarter of the 17.6 million permanent residents in the city has a car.

It took Beijing nearly half a century to hit the one-million mark for cars in 1997, from just 2,300 in 1949.

It took six and a half years to register the second million, the official Xinhua news agency said previously, and the pace of growth has continued to accelerate.

In 2008, government vehicles and all private automobiles were banned from Beijing's roads for one day each week in measures aimed at easing congestion and curbing emissions.

Beijing's air is among the most polluted in the world, and the problem is getting worse amid high demand for private vehicles from its increasingly affluent residents.

China's auto sales hit 13.64 million units in 2009, overtaking those in the United States to make the country the world's top auto market, as the government offered incentives such as lower taxes to boost the sector.