Black smoke hung over parts of this palm-fringed seaside capital today and troops patrolled burned-out neighborhoods and searched charred buildings for bodies after four days of communal violence, as the options for dealing with the country's problems in moderate terms seemed to be evaporating.

A curfew imposed to halt the violence that has taken an estimated 100 lives throughout the country was lifted at 6 a.m. today but was reimposed at 4 p.m., apparently to prevent the warring ethnic factions from preparing new attacks. The government, which has clamped a virtual blackout on news of the violence, except for occasional bland communiques, gave no explanation for reinstating the curfew.

Frustrated expectations of increased self-rule for the minority Tamil community of Sri Lanka, coupled with the government's fears that its support from the majority Sinhalese was slipping, appear to have been the primary combustibles that ignited the most severe violence in this scenic island nation since it declared independence from Britain in 1948.

Although terrorism, insurgencies and communal rioting have bedeviled Sri Lanka since then, never has it touched so heavily upon the capital and gripped its people with fears of worse to come.

Sri Lankans across the political spectrum today talked of indigenous Sinhalese and Tamils of Indian origin regrouping for one last, great battle of reprisals in which they would vent decades of pent-up hatred and distrust.

The terrorist bands of insurgents that have operated freely in the safety of their own havens in Sri Lanka's northern and eastern provinces displayed signs of growing confidence that they can force direct actions in Colombo and elsewhere by their own methods.

There was no more talk of roundtable "accommodation" negotiations between Tamils and the government of President Junius R. Jayewardene. With the mass resignations from Parliament of all 16 members from the Tamil United Liberation Front, there appeared to be no moderate Tamil voices left to ease tensions.

The death toll in four days of nationwide violence was unofficially put at more than 100, but nobody knows what the actual figure is. There were unconfirmed reports here today of killings of more Sinhalese soldiers in northern Sri Lanka in reprisal for the massacre of 35 Tamil prisoners in their cells on Monday, which in turn was in reprisal for the ambush slaying of 13 Sinhalese soldiers near the northern town of Jaffna during the weekend.

The government estimated that 50,000 persons, mostly Tamils, have been left homeless by the wave of arson and looting that has swept Colombo. Six refugee centers have been hastily erected, but thousands of Tamils were wandering the city with nowhere to go.

Barely 100 yards from the ornate President's House, rows of Tamil-owned stores smoldered from nighttime arson attacks, and not far away fires burned, unattended by an overworked municipal fire department.

Witnesses to the last two nights of violence here said that some streets were littered with corpses, some of which had been mutilated with x's or burned. They said virtually all of the victims were Tamils.

"It is a case of being burned inside your house or being killed outside," one Colombo resident said.

The worst violence erupted Sunday night after the Army, in a move whose judgment has been widely questioned, brought the bodies of the 13 Sinhalese soldiers killed near Jaffna here for a mass burial. A large crowd gathered at the ceremony and demanded that the soldiers be buried separately by their own families, and the attack on Tamil neighborhoods began shortly after.

Violence that broke out today in the town of Kandy was attributed to emotional outbursts following the cremation of three of the Sinhalese soldiers there.

Some political observers here expressed bewilderment over Jayewardene's failure to make any public appeals for peace. The state-owned radio and television have been silent about the violence, except for broadcasting terse communiques and deleting Tamil-language programs in favor of English ones.

Jayewardene remains very popular among the Sinhalese, who make up 73 percent of the population of 14.5 million, despite some loss of favor because of rising inflation and resentment over the government's inability to resolve the Tamil problem once and for all.

He was overwhelmingly elected to a six-year term in October, his United National Party has a 56 percent majority in the Parliament and last December a national referendum extended the life of the Parliament.

While the Sri Lankan Army traditionally has been given relatively free rein in putting down insurgencies and civil disorders, some political observers here attributed the president's lack of public involvement in the crisis to his reluctance to antagonize his own supporters by appearing to appease the Tamils, who make up about 20 percent of the population.

The Tamils have sought to establish a separate state in northern Sri Lanka. Although his efforts were largely sidetracked by eight months of elections and the referendum, Jayewardene has done more more than any of his predecessors to attempt to develop a semblance of autonomy for Tamils through a plan of elected district development councils.

As a result of those efforts, expectations had risen among the 3.5 million Tamils that Jayewardene's government might accomplish what other governments had failed to do in increasing Tamil education and job opportunities and resolving the long-simmering language issue.