Standard & Poor's said on Wednesday that its ratings of China Petroleum & Chemical Corp and its parent, China Petrochemical Corp, were not affected by the explosion at Sinopec Corp's crude oil pipeline at Qingdao, Shandong province, last week.

"We believe the group's sound financial strength and liquidity, and its diversified asset base, will limit any credit impact," said Gloria Lu, primary credit analyst at S&P.

The accident could hit the operations and financial performance of both companies, but details about the losses are not yet available.

The pipeline explosion could affect oil supplies to the group's refineries in Qingdao, and reconstruction will be costly. But a possible change in the group's senior management in the wake of the accident is unlikely to materially affect operations, S&P said.

"Our ratings on Sinopec Corp and Sinopec Group can withstand severe downside scenarios," Lu said.

"According to our criteria for rating government-related entities, we assess that the likelihood that both companies will receive extraordinary support from the Chinese government is extremely high."

S&P may lower the ratings if the stand-alone credit profiles of the companies, currently at A-minus, deteriorate to B-plus or lower, Lu said.

According to the report, the possibility of that happening is remote.