Meftah Daouadi was being taken to Tunisia for unspecified medical treatment, Libya’s government said.
He was part of the 2011 uprising against Muammar Gaddafi before working at the Ministry of Martyrs, which looks after the families of former fighters.
The Antonov plane is said to have suffered engine failure.
It came down in a field near Grombalia, about 40km (25 miles) south of the capital, Tunis.
As well as Mr Daouadi, three doctors, six crew and another patient died, a Tunisian rescue worker said.
“The whole plane was completely burnt out. The emergency services went to the crash site and recovered the charred bodies,” said emergency services spokesman Mongi El Kadhi.
The BBC’s Rana Jawad in Tripoli says Libyans often get medical treatment in Tunisia as standards are higher.
Mr Daouadi was a leader of the now disbanded Libyan Islamic Fighting Group, which was accused of having links to al-Qaeda, reports the AFP news agency.
Source: BBC News
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