PHNOM PENH - Authorities in Cambodia have issued a stern rebuke to students to avoid "inappropriate activities" this Valentine's Day, warning them of the perils of "losing dignity".

Valentine's Day has become popular among young people in many Southeast Asian countries in recent years, with bunches of red roses and heart-shaped chocolates popping up in stores and on street stalls in the days leading up to February 14.

While some might see the annual celebration of love as a bit of harmless fun, the Cambodian government — which has form for issuing dire warnings about the pitfalls of young love and premarital sex — is rattled.

The education ministry issued a directive to public and private schools late on Tuesday ordering them to "take measures to prevent inappropriate activities on Valentine's Day".

"It is not tradition of our Khmer nationality," the statement said.

The ministry also noted that the event had made "a small number of youths... forget about studying and lose the dignity of themselves and their families".

The ministry of culture called on authorities and parents "to remind children to use the day in line with the beautiful Khmer tradition for the sake of their honour and dignity".

And the ministry of women's affairs weighed in, saying some people "misunderstand the meaning of February 14".

Cambodia's National AIDS Authority warned that AIDS was still spreading and that some people, particularly youth, used Valentine's Day to "show love that leads to possible sexual intercourse".

Last year, there were 7,600 people living with AIDS in Cambodia, including 1,400 new cases, it said.

About 42 percent of the new cases are youths aged between 15 and 24, the authority said.

Social conservatives see Valentine's Day as a foreign import that represents a moral threat to traditional Buddhist beliefs.

Cambodian women in particular are under intense social pressure to retain their virginity until marriage.