A Polish volunteer who died of wounds sustained during a humanitarian mission in eastern Ukraine was buried in his home city in western Poland Friday.

Marek Mastalerz of the Inicjatywa Nehemiasz (Nehemiah Initiative) private aid group is the first Polish volunteer known to have been killed in neighboring Ukraine since Russia started the war there 14 months ago.

A number of Polish activists have been injured while taking aid to Ukraine.

Mastalerz, in his mid-40s, was buried in a Roman Catholic service in Poznan, according to the volunteer group.

Mastalerz and another volunteer, a Ukrainian man living in Poland, were injured March 16 in a Russian missile attack on Konstiantynivka, a town some 17 miles southwest of Bakhmut.

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A Polish volunteer who died from injuries sustained in a humanitarian mission has buried at home in western Poland. (Fox News)

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Mastalerz died of his injuries on March 27 in a hospital in Kyiv. The Ukrainian volunteer was evacuated to Poland and is recovering.

"Both volunteers knew where they were going. They both knew the risk. Still, they took it, in order to deliver humanitarian aid and encouragement to the fighting Ukrainians," Inicjatywa Nehemiasz said on Facebook.

It stressed they have both gone though security and first aid training.

The group members are setting off on another mission for Ukraine on Saturday.

European Union and NATO member Poland has been a major supplier of military, political and humanitarian support to Ukraine.