The UNHCR resumed, on Friday, a stalled programme of family-visit flights with a flight from Smara to Tindouf after "well-coordinated efforts with all parties involved," said a statement of the UN body.

"To our disappointment, the 20 passengers on the flight were prevented from disembarking by the polisario representatives in Tindouf," the statement says, adding that "the UNHCR had no choice but to fly the passengers back to Smara".

UNHCR said it is seeking to clarify with the Polisario the reasons for the refusal of disembarkation, noting that "Friday's flight was aimed at restarting the programme and was the result of intensive but constructive negotiations with Morocco and the polisario."

"Family-visit flights are an important element in a Confidence Building Measures programme that has been in place since 2004," the UNHCR said.

"It is our hope that the Confidence Building Measures programme will be able to resume at the earliest opportunity," the UNHCR underlined.