CNOOC's (SHA:600938, HKG:0883) actual controller, China National Offshore Oil Corporation, further raised its shareholding in the listed company with purchases totaling 652.2 million yuan, according to a Thursday filing with the Hong Kong Stock Exchange.

The state-owned parent company acquired 3.8 million Shanghai-listed A-shares for 130 million yuan and 31.8 million Hong Kong-listed H-shares for 522.2 million yuan.

Combined, the newly acquired shares account for 0.08% of CNOOC's total share capital.

Despite the purchases, the company said that halfway through the originally scheduled period for the shareholding increase plan, the aggregate amount has not yet reached 50% of the planned lower limit. CNOOC attributed the lag to overseas geopolitics, significant fluctuations in international crude oil prices, and capital market changes.

The parent company confirmed it will continue to increase its stake "at appropriate opportunities" using internal funds.