They said the unionists claimed the toll in the name of donation for one of their ailing colleagues when senior officials of the Unocal were holding a meeting with the management of Bangladesh Oil, Gas and Mineral Resources Corporation at Petro Centre on Wednesday.

The Unocal officials, including director (finance) and general manager (operations), tried to make the union leaders understand that the US company legally and ethically was not in a position to make any such "unlawful payment".

As the unsatisfied union men showed rough attitude, the sources said, the senior officials of Petrobangla could manage them.

The sources said that the "extortion" bid came after the Unocal had turned down a previous demand for a handsome amount of money.

Senior officials at Petrobangla are upset over such a demand to a major foreign investor, that too at a negotiation meeting on gas supply from Moulvibazar-2 field.

"It'll certainly discourage foreign investors like an oil giant Unocal from making investment in the energy sector for which the country is trying hard," said a senior Petrobangla official.