Ja.
thisisathens.org "In Kirchen und in Kathedralen... Gläubige dürfen an Gottesdiensten teilnehmen (Kapazitätseinschränkungen sollen eingehalten werden) und sind verpflichtet doppelte Masken zu tragen..."

eKathimerini 24.04.: Worshippers must wear double masks during church services over Easter Week according to the rules announced on Friday Deputy Civil Protection Minister Nikos Hardalias... The use of a double mask by worshippers is mandatory both indoors and outdoors, he stressed. Moreover, self-tests are also obligatory for priests, nuns and other staff who will be inside the church..."

LG, Tom