The Italian Chapel, on the island of Lamb Holm in Orkney, was constructed by Italian prisoners of war during the Second World War.
The three stolen plaques were among 14 gifted to the chapel by its creator, Domenico Chiocchetti, when he returned to visit with his wife in 1964.
It was initially thought they were stolen sometime between Tuesday July 29 and Tuesday August 12 but officers have now narrowed the time of the theft to between 9am on Wednesday August 6 and 5.40pm on Friday August 8.
Awareness of the theft has been spread on social media across the world and police have now appealed directly to those responsible to "think again about their actions and to take every step to ensure the plaques are found and returned to their rightful place within the chapel".
Mr Chiocchetti, who died in 1999, was from Moena in northern Italy.
Each plaque is made of mahogany and measures around 6in x 8in (15cm x 20cm), with a cross on top.
They depict the Stations of the Cross - the journey of Christ to the cross - and are individually numbered with Roman numerals. The missing plaques are numbers IV, VI and X.
John Muir, secretary of the Italian Chapel Preservation Committee, said the theft had caused much upset.
He said: ''The plaques are very significant because it was a personal gift from the artist who brought them over when he first took his wife to Orkney.
''They were carved in his own town and he brought them over as a personal gift. It's devastating to think that someone would lower themselves to steal three of the plaques.
"People are very, very upset. Everyone I've spoken to this morning has expressed expressed their disappointment and disgust at the situation."
A Police Scotland statement said: "Police in Orkney would like to thank everyone who has come forward with information and photographs surrounding the theft from the Italian Chapel.
"The huge level of response from all over the world shows the respect and affection held for this historic place of worship and the level of outrage that someone has chosen to steal from within its walls.
"Anyone with information regarding who is responsible or the current whereabouts of the plaques can contact the police on 101. Alternatively, information may be passed confidentially to Crimestoppers on 0800 555 111."