US authorities have released two Pakistani brothers, Abdul and Mohammed Rabbani, from the military prison at Guantanamo Bay after over 20 years of detention. 

The Rabbani brothers, who were arrested on suspicion of al-Qaida links, arrived in Pakistan on Friday, officials said. 

Mushtaq Ahmed Khan, the chairman of the human rights committee in the upper house of Pakistan's parliament, said the pair had reached Islamabad airport. 

The two men were "innocently imprisoned in Guantanamo Bay for 21 years. There was no trial, no court proceedings, no charges against them," Khan wrote on Twitter. "Congratulations on their release. Thank you Senate of Pakistan." 

Why were the Rabbani brothers detained?

Mohammed Rabbani was accused of organizing travel and funds for senior al-Qaida members, and recruiting his brother into extremist circles.

US officials had accused Abdul Rabbani of working for the avowed mastermind behind the September 11, 2001, terrorist attacks on the US. He was also accused of operating an al-Qaida safe house in Karachi, Pakistan's largest southern port city.

According to his detainee assessment, however, he was not believed to have had "specific insight into al-Qaida operational plans."

Pakistani authorities arrested the two men in 2002, and were in CIA custody before being transferred to Guantanamo.

A US Senate report said Mohammed Rabbani was one of 17 detainees subjected to torture at overseas CIA secret prisons.

According to the US Defense Department, the pair were approved for release in 2021.

Their release is the latest move toward emptying the Guantanamo Bay detention facility, which has had a reputation for severe human rights abuses and inhumane interrogation techniques.

Some 32 detainees are still at the military prison — only two of them have been convicted. 

fb/rt (AP, AFP)