The International Committee of the Red Cross (ICRC) gained access to both Ukrainian and Russian prisoners of war last week and more visits are planned in what it described in a Thursday statement as "important progress".
Since Russia invaded Ukraine in February, the Geneva-based body has reached hundreds of prisoners on both sides. But hitherto, that access has been "sporadic", it said.
"My expectation is that these visits lead to more regular access to all prisoners of war," the statement cited ICRC President Mirjana Spoljaric as saying.
"While the recent visits are important progress, the ICRC must be granted unimpeded access to see all prisoners of war repeatedly and in private, wherever they are held," the ICRC statement also said.
The right of the ICRC as an impartial humanitarian body to regularly visit prisoners of war is protected by the Third Geneva Convention to which both Russia and Ukraine are parties.
However, access in the Ukraine conflict has not always been granted and Ukrainian President Volodymyr Zelenskiy has in the past accused the ICRC of inaction.
The U.N. human rights office said last month that its monitors had not been allowed access to Ukrainian prisoners of war held by Russia.
The ICRC said it carried out a two-day visit to Ukrainian POWs last week, with another happening this week. It also visited Russian POWs last week and more such visits are planned by month-end. The ICRC declined to give details on the exact number of prisoners nor the locations of the detention centres.
The Red Cross is now reaching out to the family members of POWs to share updates. Some sent back short notes of love and personal news while others asked for cigarettes, sweets and socks, it said. "All these messages are a lifeline to anguished relatives."
(Reporting by Emma Farge; Editing by Raissa Kasolowsky)