The Oil and Natural Gas Corp will finalise this month the purchase of a 25 per cent stake in Sudan's controversial oil project from Canada's Talisman Energy Inc, officials said.

"An agreement has been signed with the Sudan government. Now a formal agreement has to be signed with Talisman. This will be followed by the payment of $750 million by the end of March," an ONGC official, who did not want to be named, said on Monday.

Talisman's partners in the venture -- Malaysia's state oil firm Petronas, China National Petroleum Corp and Sudan's Sudapet -- had the rights of first refusal over Talisman's stake. Officials said Petronas wanted to buy Talisman's stake.

"The agreement with the Sudanese government has removed this hurdle. It is a major step forward," the official said, adding that the acquisition was in line with energy-hungry India's policy to buy equity oil abroad.

Talisman is selling its stake after criticism from human rights and church groups, who say the project was giving the Islamist government money to continue a civil war against mostly Christian and animist rebels. Talisman says its presence in Sudan has been positive.