Australian lawyer Melinda Taylor and three of her colleagues were arrested by Libyan authorities last month. Taylor was appointed by the ICC to help prepare the defense for Saif al-Islam Gadhafi, the son of late leader Moammar Gadhafi.
Saif al-Islam was captured by rebel forces in Zintan last year. He's wanted by the ICC for alleged war crimes committed during last year's civil war. Libyan authorities maintain the right to try him in national courts.
A source inside the Libyan attorney-general's office confirmed to the BBC that Taylor and her colleagues were released.
"They are due to face the courts here in Tripoli for the final ruling [July 23]," the source said on condition of anonymity. "We expect them to come back for the hearing but if they don't, a ruling will be made in absentia."
Taylor was accused of handing sensitive documents about Saif al-Islam from one of his supporters. Tripoli had called for an apology from the ICC.
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