Nigerian oil workers' unions have threatened to withdraw their members from the troubled Niger Delta as tension built up there following the abduction of four Shell workers and a spate of attacks on oil facilities, a senior union official told Xinhua on Friday.

"They (kidnappers) must release them (Shell workers), if they don't release them and kept on harassing other people, we will withdraw oil workers from the field for their safety," said Elijah Okougbo, general secretary of the blue-collar National Union of Petroleum and Natural Gas (NUPENG).

Source: Xinhuashares worth 583.73 million ringgit (155.24 million U.S. dollars).

Source: Xinhua