Ali al-Issawi, a former number two in Libya's National Transitional Council, is a suspect in the assassination of a top general in July, Libyan TV reported on Tuesday.
General Abdel Fattah Yunis was killed in mysterious circumstances on July 28 when he was called back from the front line for questioning in the eastern city of Benghazi.
Yunis, a pillar of Moamer Kadhafi's regime, had joined the rebellion against the now dead dictator.
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The military prosecutor of NTC, Yussef al-Aseifer, listed seven names of those involved in the murder, including Issawi, according to a statement broadcast by several local channels, including Libyan TV.
"Seven people are suspected of involvement in the murder of Abdel Fattah Yunis. Three were arrested and others are sought by the security forces," Aseifer was quoted as saying by the channel.
Issawi, a former NTC deputy prime minister for foreign affairs who was one of the first of several senior diplomats to defect from Kadhafi's regime, denied his involvement in a telephone call to the channel.
The death of Yunis had provoked intense speculation over the identity of the murderers, with fingers pointed at the divisions within the former anti-Kadhafi rebels or at some remnants of Kadhafi diehards.
The NTC had launched an adminstrative and criminal probes into the murder which had received widespread criticism.