BEIJING, Thursday 2 September 2010 (AFP) - A huge traffic jam stretching at least 120 kilometres (75 miles) reappeared in northern China Thursday, with thousands of cargo trucks stuck in a bottleneck, state media said.

State television broadcast images of a long line of mostly cargo trucks inching slowly through Inner Mongolia on a major highway leading toward Beijing that has come to symbolise China's serious traffic problem.

"You could say the highway has become a big parking lot," a CCTV reporter at the scene said, estimating the number of vehicles stuck in the congestion at more than 10,000.

However, CCTV later said the congestion began to clear in the afternoon.

The stretch of highway linking Inner Mongolia and the northern province of Hebei with Beijing is among the nation's busiest as the capital of more than 20 million people sucks in huge shipments of goods.

Gridlock has become a feature of the route recently, with blame falling on highway maintenance projects and accidents.

Traffic slowed to a snail's pace in June and July for nearly a month, according to earlier press reports. In August, state media said some drivers were stuck in a huge traffic jam on the route for nine days.

The traffic subsequently cleared but has worsened again due to accidents and traffic restrictions imposed by authorities, CCTV said.

China has embarked in recent years on a huge expansion of its national road system but the volume traffic periodically overwhelms the grid.

According to government data, Beijing is on track to have five million cars on its roads by year's end. The four-million mark was passed in December.