A city environmental watchdog has lashed out against a giant petrochemical company and ordered it to apologize to the public in a rare case of government lambasting a State-owned corporation.

The environmental bureau in Lanzhou, capital of Gansu province, listed four major pollution incidents by PetroChina's Lanzhou Petrochemical Co since last August and demanded an apology.

The main incident involved a leak of ethylene that caused a fire on Aug 4 last year. Other incidents involved air pollution and the improper disposal of dangerous waste.

However, the city government seems to want more than an apology from the company. "The authority wants us to relocate," said an employee at the company who refused to be identified.

An estimated fund of 40 billion to 60 billion yuan ($6 billion to $10 billion) would be required for the company to relocate, and PetroChina has the authority to make the decision.

The relocation issue was raised in 2012 but wasn't approved by PetroChina.

"The motives behind the city government are more than curbing pollution. The government wants the company to move to a new district to boost the city's economic growth, and the price of the land that the company occupies has yet to be agreed on by the two sides," an official with the company said under condition of anonymity.

The official said PetroChina and the city government have agreed to relocate, but the two sides haven't reached a consensus on how the location fees would be paid.

Yuan Zhanting, mayor of Lan-zhou, immediately denied the claim by the unknown official and said the city doesn't have the authority to ask the company to relocate.

Lanzhou, a heavily industrialized city, ranks among China's most polluted areas. The city is plagued by pollution scandals.

The most recent one occurred in April when seepage of residual oil leaked from the integrated refinery and petrochemical complex into the water table and caused unusually high benzene levels in the city's tap water. The water supply was turned off in one district, forcing residents to buy bottled water and causing a water shortage panic.

While condemning the company's leakage of the carcinogen, local people said the city's water supply company also needed to do something.

Zhou Mou, 33, a resident of Lanzhou, said the risks of water pollution have existed since the founding of the company more than 60 years ago and he suggested another way to reduce the risk from pollution.

Lanzhou Petrochemical Co issued a statement to respond to the authority's criticism, saying that it had examined the problems put forward by the environment bureau and had taken measures to correct the irregularities.

"We take supervision from the government and criticism from society seriously," the statement said.

Contact the writer at zhang_yi@chinadaily.com.cn

Du Juan contributed to this story.