Both companies were affected by decreased crude oil prices. PetroChina's profits in prospecting and extracting activities declined 5.6 percent year-on-year to 56.98 billion yuan, while Sinopec's profits in that sector tumbled 16.99 percent to 16.23 billion yuan.

PetroChina was also hit by a natural gas import price that is often higher than the domestic sales price.

Its profits in natural gas and pipeline businesses dipped 45 percent year-on-year to 1.1 billion yuan in the first quarter, with 14.45 billion yuan of losses recorded in gas and liquefied natural gas imports.

With prices of imported crude and gas swayed by global markets but domestic retail prices under government control, Chinese oil firms must further reduce operation costs and control the scale of their investment, said Qiu.

As part of its efforts to push market-oriented pricing for energy resources, the government announced last month it would shorten the retail fuel price adjustment cycle to 10 working days from 22 working days to better reflect changes in global oil markets.

In the first quarter, both PetroChina and Sinopec posted weak profits in marketing and chemical product businesses as a slowing economy sapped demand.

PetroChina saw profits in marketing plummet 65 percent year-on-year and recorded 3.18 billion yuan of losses in chemical business, according to the company's statement.

Sinopec's profits in marketing and distribution operations slipped 11.2 percent year-on-year and those in chemical products dived 87.47 percent.

The price of PetroChina's shares in Shanghai edged up 0.12 percent to 8.52 yuan on Thursday. Sinopec's shares climbed 0.59 percent to 6.78 yuan.

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