The Popular Front for the Liberation of the Saguia al Hamra and Rio de Oro (Polisario Front) agreed on Friday to coordinate with the International committee of the Red Cross (ICRC) in repatriating the captives from its desert base in Algeria.
Qatar has not given further details about how the prisoners will be freed, but plans to continue efforts in a bid to secure more releases.
The Algerian news agency APS published the Polisario statement confirming a release – but did not give a date, though captives are usually handed over to the ICRC within a few days of an announcement.
Those released are likely to be Moroccan army officers
Good will gesture
According to the statement, the move shows the "Polisario Front's sincere wish to spare no effort to help bring about a just and definitive peace in the Western Sahara, on the basis of strict respect of the right of the Sahrawi people to self-determination."
The front had asked Qatar to intervene with Morocco to "obtain the liberation of Sahrawi soldiers and have light shed on what happened to those who have disappeared," the statement added.
Polisario says Morocco is still "holding, in total secrecy, 150 Sahrawi fighters and more than 500 vanished civilians" – according to the statement.
The release demonstrates the "Polisario Front's sincere wish to spare no effort to help bring about a just and definitive peace in the Western Sahara, on the basis of strict respect of the right of the Sahrawi people to self-determination"
The movement released 300 prisoners in November last year. Prior to Friday's announcement, it had in all freed 1,743 Moroccans in unilateral moves since the 1991 ceasefire.
The ICRC last visited Moroccan prisoners held by Polisario in the Tindouf border region in Algeria's desert southwest in December 2003, when it expressed "great concern" at their condition.
In all, the ICRC said the front was still holding 614 Moroccans, 188 of whom have been captives for more than 20 years.
The Front is a government-in-exile recognised by 54 nations and led by Muhammad Abd al-Aziz.
It agreed to a ceasefire in 1991 in return for a referendum on independence, a vote that has still not taken place.
Morocco annexed the northern two-thirds of Western Sahara (formerly named Spanish Sahara) when the Spanish withdrew in 1976.
Under pressure from Polisario guerrillas, Mauritania abandoned all claims to sovereignty of the southern third in August 1979.
Morocco then moved to occupy the southern-most sector shortly after and has since asserted administrative control.
A guerrilla war contesting Rabat's occupation was fought for 12 years, but stopped when a UN-monitored cease-fire was implemented on 6 September 1991 with the promise of a referendum on the final status of the region.
This has been repeatedly delayed through lack of agreement on who is eligible to vote.
There are currently 65,000 Moroccan troops in the Western Sahara.