QINGDAO, May 9 -- East China's Qingdao, one of the world's busiest ports, has seen unprecedented congestion, with crude oil tankers waiting for days to be unloaded, industry insiders said.

More than ten tankers were anchored off Qingdao port each day, waiting to dock, said Su Peng, an official with Qingdao Shihua Crude Oil Terminal Co., adding that the situation is something he had never seen before.

The continuous arrival of large vessels this year has led to a severe jam at the terminal, said Qingdao Shihua's general manager Liu Jin.

The oil pipeline linking Huangdao in Qingdao and the neighboring city of Weifang is working at its maximum capacity of 45 thousand tonnes a day, 112.6 percent more than last year, Xinhua learned.

The movement of crude oil on Qingdao port highway stands at one million tonnes per day, 65.1 percent higher than last year. The railway has seen 25.4 percent higher operation than last year.

Crude oil imports in ports across Shandong Province, where Qingdao is located, rose 78.2 percent in the first quarter compared with last year, according to customs statistics.

"Big vessels are jamming big ports, and small vessels are jamming small ports," said Sun Chenglin, logistics manager of Shandong Chambroad Petrochemicals Co., Ltd., a major privately owned oil refiner.

The congestion is expected to be alleviated after June, authorities with Qingdao port told Xinhua, after analyzing its major customers involved in crude transport.

Cargo traffic rose to 497 million tonnes last year at Qingdao port, the world's seventh largest.