In a statement - a copy of which has been received by Aljazeera - the rights monitor said the body of al-Ghazal was found in Qanfudha area, west of Benghazi.
Al-Raqib's statement also said the body bore signs of injury and that the report of the medical examiner showed that al-Ghazal had been tortured.
Al-Ghazal, who was a contributor to al-Zahf al-Akhdar (the Green March) publication and a member of the Revolutionary Committee, was forced to stop writing in Libyan newspapers after he strongly criticised the government of Muammar al-Qadhafi.
His most hard-hitting pieces appeared in the left-leaning paper, Libya Today.
Earlier in the week, the human-rights group had expressed fear that he might have been killed by "extremists in the revolutionary committees movement" because of his harsh criticism of the movement.
French Minister Alliot-Marie (R)
called for more press freedom
In a press statement, al-Raqib had said it held the Libyan government responsible for al-Ghazal's disappearance, for it was well known that he had received several death threats.
The organisation said al-Qadhafi's government often silenced journalists it considered a nuisance.
On a recent trip to Libya, the French Defence Minister Michelle Alliot-Marie criticised the Libyan authorities for the lack of media freedom in the country.
Al-Ghazal's writing frequently attacked government corruption and called for reforms.
The Libyan government has in the past taken action against authors of critical articles, citing threats to the country's security and stability.
Al-Ghazal had worked for four years with al-Zahf al-Akhdar newspaper. His articles appeared in other Libyan dailies too.
Earlier, he had announced he would boycott all newspapers run by the Libyan government, saying his decision stemmed from his desire to "correct the path" of his country.