Dutch Jesuit Father Frans van der Lugt was allegedly shot dead Monday in the besieged city of Homs, an activist group reported.
The Syrian Observatory for Human Rights said he was shot dead inside a monaster in the Bustan al-Diwan neighborhood.
Having lived in Syria for decades, Father van der Lugt had been a major champion of the plight of the people of Homs, who have been living under regime siege for two years now.
Motives for the attack were not immediately known.
During the three-year civil war, van Der Lught repeatedly refused to leave Bustan al-Diwan, a rebel stronghold that has been blockaded by forces loyal to Syrian President Bashar Assad for the past year.
"The Syrian people have given me so much, so much kindness, inspiration and everything they have. If the Syrian people are suffering now, I want to share their pain and their difficulties," he said.
He stayed on even as some 1,400 people were evacuated during a UN-supervised operation that began on February 7 and also saw limited supplies of food brought into the city.
Homs's Old City, under rebel control, has been besieged by government forces for nearly two years, creating increasing dire circumstances for those unable to leave.
"The faces of people you see in the street are weak and yellow. Their bodies are weakened and have lost their strength," Van der Lugt told AFP before the UN operation.
"What should we do, die of hunger?"
The siege and continued shelling in the city whittled away the Old City's population, including a Christian community that shrunk from tens of thousands to just 66, according to the Dutch priest.
A Jesuit, Father Frans arrived in Syria in 1966 after spending two years in Lebanon studying Arabic.
In early 2014, some aid was allowed into the Old City of Homs, and some trapped civilians allowed out, but thousands remain, living in extremely difficult conditions and with severe food and medical shortages.
Source: The Daily Star