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The former Libyan intelligence agent convicted of the 1988 Lockerbie bombing over Scotland that killed 270 people made a rare public appearance on Tuesday at a rally in support of Muammar al-Qaddafi, a "further reminder that a great mistake was made when he was released," British Foreign Secretary William Hague said.

Abdel Basset al-Megrahi, who returned to a hero's welcome in Libya in 2009 after being released from a Scottish jail after being diagnosed with terminal prostate cancer, appeared on Libyan state television wearing traditional local garb while sitting in a wheelchair at a tribal meeting in Tripoli.

Al-Megrahi was convicted in the 1988 downing of Pan Am Flight 103 that killed 270 people, most of them Americans, over Lockerbie, Scotland.

While announcing that Britian would officially recognize Libya's opposition governing council on Wednesday, Hague reiterated the current British government's fury over the freeing of Al-Megrahi after he was pictured at the rally. Hague scathingly described the medical advice that led to the 59-year-old's release on compassionate grounds as "pretty worthless."

"The appearance of Mr. al-Megrahi on our television screens is a further reminder that a great mistake was made when he was released," Hague said. "This was absolutely the wrong thing to do."

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Hague said Britain is unfreezing $150 million of Libyan oil assets to help the rebels' National Transitional Council, which the U.K. now recognizes as "the sole governmental authority in Libya."

Hague said the council had been invited to send an ambassador to London, adding that "we will deal with the National Transitional Council on the same basis as other governments around the world."

Qaddafi has ruled Libya for more than four decades.

In February, anti-government protests erupted in the country, inspired by uprisings elsewhere in the Arab world, but quickly escalated into civil war. However, the conflict has been deadlocked for months, with rebels controlling the east of the country in the west, and Qaddafi clinging to power in the remaining areas.

The Associated Press contributed to this report.