"Two members of Al-Qaeda in the Islamic Maghreb (AQIM) who allegedly took part in Mr Lazarevic's abduction have previously been named as having been released - Malians Mohamed Aly Ag Wadoussene and Haiba Ag Acherif.
"The Malian Human Rights Association told the BBC's Alex Duval Smith in Bamako it had learned that a further two militants, Tunisian national Oussama Ben Gouzzi and Habib Ould Mahouloud, from Western Sahara, were released last week."
The justice minister said a similar deal had been done to free about 30 of its nationals who were captured in the northern city of Kidal, a stronghold of Tuareg separatists, according to Reuters.
"Lazarevic was snatched by armed men in Mali on November 24, 2011, while on a business trip with fellow Frenchman Philippe Verdon in a kidnapping claimed by al Qaeda in the Islamic Maghreb (AQIM).
"Verdon, who suffered from an ulcer and tachycardia – an abnormally fast heartbeat – was found shot dead last year, and those close to his family suggested he had been executed because he was weak."