SAVUR MOHYLA, DONETSK, EASTERN UKRAINE - As the cease-fire becomes more fragile in eastern Ukraine, a team of volunteer body collectors travels to the small village of Savur Mohyla in the what pro-Russian separatists call the Donetsk Peoples Republic - to retrieve bodies of fallen Ukrainian servicemen from rebel-held territories.

With a recent escalation in violence in eastern Ukraine's separatist conflict, the number of dead grows.  Many fallen soldiers are buried without record, often in a grave without a name or tombstone. On the road to the village of Savur Mohyla near the Russian border, a Ukrainian volunteer team called Black Tulip is on a mission to collect bodies of fallen Ukraine government soldiers from rebel-held territory.

Little remains of the military positions that were here. But there is still danger from land mines and booby traps.  Still, the team does this grim work without pay.

"There is one body here, we received information from local citizens, it was a fight over here in the end of August.  Ukrainian soldiers were pushed back and one of the soldiers was left here," said Black Tulip volunteer Aleksey.

Despite coming from Ukrainian government-held territory,  the team is able to work in separatist-controlled land through cooperation with the militaries on both sides.

"We transmit bodies from the Ukrainian side to the DNR  [separatist] side and vice versa.  There is an agreement between the government of DNR and the Ukrainian Ministry of Defense, and when this agreement is confirmed, on that day we are able to cross the border," said Aleksey.

The separatists' commissioner for missing people, Lilia Radionova, helps coordinate the team. She says she gets thousands of request every day to help find missing persons - her desk piled with letters and photos from family members.

"I received a lot of phone calls from Ukrainian soldiers' relatives, mothers, fathers, wives. This is a Ukrainian soldiers' list of lost in action," said Radionova.

Although February's cease-fire agreement called for returning casualties and prisoners of war, getting permission for the team to work can be difficult.  But Radionova says cooperation between the two sides is improving.

"When we submitted 22 bodies to them from Donetsk airport something changed, after this ultimatum we demanded something changed.  Since January, we could not take our fallen from Volnovakha and now finally we received the bodies, thanks to them but at the moment there are many more bodies...Due to joint efforts we will have an agreement in future," she said.

The volunteers return with a body they think may be a rebel soldier. They say they will hand it to authorities for identification.

"We apply visual inspection of the body, sometimes there are some documents in pockets and we can use it to identify a person. If there are no documents, the only help is DNA analysis," said Aleksey.

More than 6,000 fighters and civilians have died in the conflict in eastern Ukraine over the past year, and with frequent cease-fire violations, the team's work is far from over.