Sinopec Corp (SHA:600028, HKG:0386) and Shenhua Energy Co (SHA:601088, HKG:1088) said today their state-owned parents have increased stakes in the listed arms in a move analysts said intended to boost share prices and investor confidence.

Sinopec, China's largest oil refiner, said its parent, China Petrochemical Corp (Sinopec Group), has bought 39 million yuan-denominated Shanghai-listed A shares and 425 million Hong Kong-listed H shares, enlarging its holdings from 75.84 percent to 76.38 percent.

"This could reassure investors about the firm's restructuring potential under new Chairman Fu (Chengyu) and help the stock extend its outperformance," Mirae Asset Securities analyst Gordon Kwan wrote in a note.

Shenhua's parent, Shenhua Group, bought 10.8 million A shares, lifting its stake in the country's biggest coal producer to 73.01 percent from 72.96 percent.

The moves came as the Shanghai Composite Index shrank by more than one fifth last year, making the Chinese market one of the worst performers globally.

Shanghai-listed China United Network Communications Ltd said its parent increased its stake from 61.05 percent to 61.07 percent and plans to buy up to 2 percent of the listed company's total shares in one year.