State-run explorer Oil and Natural Gas Corp said its overseas arm has agreed to buy an additional 12 percent stake in a Brazilian oil block from Brazil's Petrobras for $529 million.
Petrobras had earlier agreed to sell its 35 percent stake in the block to China's Sinochem Group for $1.54 billion, but the deal was subject to pre-emption rights of ONGC and Royal Dutch Shell .
Shell is the operator of the block with a 50 percent stake, while ONGC already owns 15 percent of the block.
Shell and ONGC Videsh served a pre-emption notice on September 17 to jointly acquire the 35 percent stake, ONGC said in a statement to Indian stock exchanges on Monday.
Reuters last month reported that the companies were planning to exercise their pre-emption right on the stake.