SINGAPORE -- From the outside, this prosperous island city-state is Asia's model melting pot: "A Nation For All," as this year's Independence Day slogan proudly proclaims.

But a series of incidents here has forced Singaporeans to confront issues of race and religion, and officials have voiced unusually candid concerns in recent weeks that internal and external pressures could disrupt the appearance of ethnic harmony.

The latest controversy surrounds the government's fear that the involvement of Catholic lay workers in leftist organizing might politicize other groups, notably the predominantly Moslem Malays, who make up 15 percent of the population. Amid a surge of Islamic fundamentalism in neighboring Malaysia, the government here has publicly questioned the loyalties of Singapore's ethnic Malays.

Such issues are old here. But the intensity of discussion in the press and in interviews with government officials, diplomats and dissidents suggests a new urgency and a recognition that after 22 years of independence Singapore remains more ethnically divided than the government would like.

"We are seemingly prosperous and peaceful, but let us not forget the ultimate vulnerability of Singapore," said one government official close to Prime Minister Lee Kuan Yew. "Any concerted effort can spark racial tension."

"You look at Singapore and see a western-style democracy. We dress western, we act western," said another high-ranking minister. "But there are some deep, emotive pools that can never be wiped out -- race, language and, in the case of the Malays, religion. These are very deep and abiding loyalties."

In an Aug. 9 Independence Day message, Lee warned that "once religion crosses the line and goes into what they call social action, liberation theology, then we are opening up Pandora's box in Singapore."

Lee's message was most specifically directed to the Catholic church, which saw several of its lay workers arrested in May for involvement in what the government claims was a Marxist conspiracy.

But Lee also aimed his remarks at Islamic clerics and at a recent influx of American-influenced Christian fundamentalists, who have angered some Malays here by trying to convert Singaporean Moslems, according to diplomats and Singaporean officials.

As part of his concern about the politicization of religion, Lee said he recently barred four Moslem preachers from entering Singapore because they had incited Malays here to militancy during earlier visits.

Government officials privately said they are worried about a growing Moslem resurgence in Malaysia and about the Malaysian government's ability to control Islamic extremism.

As an island city-state of 2.6 million people -- three-quarters of them Chinese -- Singapore is sensitive to its potentially vulnerable position between two large Malay-Moslem nations, Malaysia to the north and Indonesia to the south. Singapore's population is about 58 percent Buddhist, 16 percent Moslem, 12 percent Christian and 4 percent Hindu.

The country's racial mix stems from 100 years as a British colony. Britain encouraged massive Chinese and Indian immigration. Now, 22 years after Singapore became independent from Malaysia, the government still grapples to maintain peaceful relations among its races and prevent a repeat of racially motivated rioting here in the 1950s and early 1960s.

The recent warnings about the dangers of mixing religion with politics have followed two controversies involving the Malay community.

The first was sparked by an official visit here last November by Israeli President Chaim Herzog. That visit prompted huge protests from outraged Moslems in neighboring Malaysia, who saw the visit by the leader of the Jewish state as an affront to Islam. They demonstrated at the narrow causeway linking the two countries. When Singaporean Malays also protested, Lee questioned whether they were loyal to Singapore or took their cues from Malaysia.

Earlier this year, Lee's son and trade minister, Brig. Gen. Lee Hsien Loong, opened an emotional debate here by saying Malays played a limited role in the Singaporean armed forces because "we don't want to put any of our soldiers in a difficult position, where his emotions for the nation may come into conflict with his emotions for his religion."

Such statements have rankled many Singaporean Malays, most of whom were born here. "All we ask is that we be treated like Singaporeans," said an outspoken Malay lawyer, a Moslem.

To demonstrate their loyalty, more than 200 Malay community leaders and others went last month to Orchard Road, the central downtown thoroughfare, to sign their names in a ceremonial pledge book set up for Independence Day.

The government had already raised some suspicions among Malays by the prime minister's new campaign to boost the country's population by using tax incentives and other measures to encourage people -- particularly better educated and more affluent people -- to have more children.

Some Malays and Indians interviewed said they believed that the policy was aimed at encouraging the Chinese, who tend to have the country's highest education and income levels, to boost their population.

Race relations have been helped by the country's dynamic economic growth and some constitutional guarantees for the country's Malays, such as free education.

At the same time, the government is using the race issue to justify tight restrictions on expression and dissent and tough controls on the foreign and local press. Even though the situation here is far different from that in Sri Lanka, government officials invariably raise the ethnic violence in that island nation as an example of what they fear most for Singapore.