BEIJING (AFP) – Thousands of vehicles were bogged down Monday in a more than 100-kilometre (62-mile) traffic jam leading to Beijing that has lasted nine days and highlights China's growing road congestion woes.

The Beijing-Tibet expressway slowed to a crawl on August 14 due to a spike in traffic by cargo-bearing heavy trucks heading to the capital, and compounded by road maintenance work that began five days later, the Global Times said.

The state-run newspaper said the jam between Beijing and Jining city had given birth to a mini-economy with local merchants capitalising on the stranded drivers' predicament by selling them water and food at inflated prices.

That stretch of highway linking Beijing with the northern province of Hebei and the Inner Mongolia region has become increasingly prone to massive jams as the capital of more than 20 million people sucks in huge shipments of goods.

Traffic slowed to a snail's pace in June and July for nearly a month, according to earlier press reports.

The latest clog has been worsened by the road improvement project, made necessary by highway damage caused by a steady increase in cargo traffic, the Global Times said.

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

The congestion was expected to last into mid-September as the road project will not be finished until then, the newspaper said.

The roadway is a major artery for the supply of produce, coal and other goods to Beijing.