The minority Shi'ite community in Sunni Muslim-majority Malaysia has been subject to discrimination and persecution by authorities, human rights groups have said.
State religious departments have raided the community's places of worship and made arrests.
The Selangor Islamic Religious Department, or JAIS as it is known by its Malay-language acronym, said in a weekly sermon that Muslims should not be influenced by practices of the Shi'ite sect.
Sermons in Malaysia are standardised, and Islamic leaders typically deliver their Friday sermon in mosques based on the weekly sermon issued by the state religious department.
"I implore upon the Muslim ummah (community) to always remain vigilant upon the spread of Shee'ah deviant teachings in this nation," the department said, according to a copy of the sermon posted on its website.
JAIS is the Islamic religious authority in Selangor, Malaysia's richest state. It is funded by the state government.
The Shi'ite ideology "ensnares its victims" through educational institutions, children's books, novels, comics, among others, the department said in the sermon said.
"The Muslim ummah must become the eyes and the ears for the religious authorities when stumbling upon activities that are suspicious, disguising under the pretext of Islam," it said.
The department described Shi'ite practices as "extremist" and "nauseating".
Reuters could not establish if the sermon criticising Shi'ites was delivered at all mosques in the state. But religious experts said mosques typically follow the sermon issued by the state religious authority.
Isham Pawan Ahmad, an associate professor at the International Islamic University near Kuala Lumpur, said the sermon delivered at a mosque he went to in Selangor on Friday was similar to the one issued by JAIS.
"This is the most vehement comment on Shi'ites in Malaysia. It makes them a target," Isham said.
Shi'ites are a minority is Malaysia, with some estimating their numbers in only the tens of thousands.
Shi'ite community leaders were not immediately available for comment.
In 1996, a Malaysian Islamic body issued a fatwa, an Islamic ruling, recognising Sunni Islam as the faith of Malaysian Muslims.
Malaysian Shi'ite Muslims have complained about their inability to worship freely, and that they may face obstacles in carrying out rituals which are both cultural and religious, the U.N. special rapporteur in the field of cultural rights said in a preliminary report in 2017.