China's main share index fell 4% to a 12-month closing low on Friday, dragged down by a fall in PetroChina shares and growing concerns about the economy.
The Shanghai Composite share index dropped 3.97% to finish at 3,095 points on the Shanghai Stock Exchange.
Shares in PetroChina fell 5% to 16.02 yuan, below the price at which it first floated last October.
Investors are worried that higher oil prices will trim profits at the company's petrol operations.
As PetroChina is China's largest listed company, analysts said it was inevitable that its decline would hit wider market sentiment, dragging down other stocks.Chinese investors are also said to be concerned at the government's continuing efforts to cool both inflation and growth at a time of global economic uncertainty.