A senior jail official in Bangladesh says two influential opposition leaders have been executed for committing war crimes during the country's 1971 independence war against Pakistan.

Senior Jail Superintendent Mohammad Jahangir Kabir told The Associated Press early Sunday that Bangladesh Nationalist Party leader Salahuddin Quader Chowdhury and Jamaat-e-Islami Secretary General Ali Ahsan Mohammad Mujahid were executed at 12:55 a.m. at Dhaka Central Jail in the nation's capital.

Kabir says, "They have been hanged together, at the same time."

The nation is on high alert and security has been strengthened near the jail and elsewhere to avoid violence.

The two men were convicted by a special tribunal in 2013 on charges including genocide, rape and torture during the 1971 war. U.S. lawmakers and human rights groups say the tribunal proceedings were flawed.