(Adds another scuffle, paragraph 7)

CHENGDU, China, May 23 (Reuters) - Desperate survivors of China's devastating earthquake have held up volunteer vehicles bringing in relief supplies, in one case at gunpoint, Chinese and foreign sources in Chengdu said.

Most relief teams now travel in convoys.

"We argued with them, telling them that if they took all our food other people wouldn't get any," said one volunteer from Sichuan, whose team of friends has been bringing supplies to stricken regions since the earthquake hit on May 12.

"In the end, they gave half back to us," the volunteer said of last week's hold-up.

In the first week following the quake, with everything buried under rubble and damaged buildings too dangerous to enter, survivors strictly rationed food and water. As roads have opened, the army has been able to truck in supplies, but many refugees are still surviving on instant noodles or one meal a day.

About 5 million people have been left homeless by the 7.9 magnitude quake that killed at least 55,000 people.

In Deyang, north of Chengdu, an angry crowd of hundreds massed near a store suspected of selling food, water and other supplies that had been earmarked for quake victims. The protesters later overturned a police car, video on Hong Kong Cable TV showed.

Roads were briefly closed last week to non-official vehicles, after unprepared volunteers impeded rescue work. But controls have been relaxed again, allowing volunteers and civic groups with proper passes to once again supplement the food depots provided by the army.

Several thousand people in Luojiang, near Deyang, recently surrounded a truck delivering goods meant for quake relief to a store for sale, and flipped a police car, Hong Kong's Ming Pao newspaper reported. A deputy police chief was sent to hospital. (Reporting by Lucy Hornby, additional reporting by John Ruwitch in Hong Kong; Editing by Ken Wills and Roger Crabb)

AlertNet news is provided by