LONDON -- As Britain increased its troop strength in Northern Ireland again yesterday, Prime Minister John Major flew unannounced into Belfast, toured bomb-wrecked areas of the city's center and threatened the "unspeakable" Irish Republican Army bombers with eventual capture.
The bombers who killed seven Protestant workmen Friday, he said, would be "hunted and hunted and hunted for the rest of their days until we find them."
His visit coincided with the third increase in British troop strength in two weeks as Northern Ireland edged closer to a state of prevalent fear and violence similar to that which it lived through in the early 1970s.
Peter Brooke, Mr. Major's secretary of state for Northern Ireland, told the House of Commons that in addition to troops sent over the weekend, believed to be of battalion strength, "extra troops are also now in the province" to improve vehicle checks in County Fermanagh.
(Mr. Major said yesterday that he rejected an offer by Mr. Brooke to resign. The secretary had provoked Northern Ireland Protestants by singing a folk song on Irish television shortly after the seven Protestants were killed in Friday's bomb blast.)
The British troop level in Northern Ireland is well over 17,000. It was first increased earlier this month with the call-up of reserves from the Ulster Defense Regiment, a home-grown, mostly Protestant unit within the British army, as a response to the IRA's repeated bombing of the center of Belfast.
The army then placed what was described as "a ring of steel" around the city, imposing security checks on virtually all vehicles entering Belfast. The IRA turned its attention to targets outside Belfast.
Before and during Mr. Major's brief visit yesterday, there were five bomb alerts in Belfast and four outside the city, mostly hoaxes. Tension continued to run high across the six counties as funerals were held for six of the seven men killed Friday night by the IRA bomb that exploded under their van as they traveled a country road in County Tyrone, near Cookstown.
The men were all construction hands, killed, the IRA said, because they were doing work for British security forces in Omagh.
The IRA began targeting civilians working for the security forces seven years ago. So far, they have killed 26. Some firms have placed ads in local newspapers declaring that they do no work for the government.
The nationalist, or Catholic, community braced yesterday for reprisal attacks by illegal Protestant loyalist forces.
Chief Constable Hugh Annesley of the Royal Ulster Constabulary, the province's 8,000-strong, militarized police force, said he expected the situation in Ulster of "get slightly more serious."
Patsy McGlone, a former secretary-general of the largest nationalist Catholic party, the Social Democratic and Labor Party, said the violence is a sign of "a conscious decision by the Provos [IRA] to up the ante.
"It seems to the rest of us they are going crazy . . . beyond any rationale. They say they're advocating Irish union. How do you advocate unity by murdering people?" he demanded.
During his visit to Belfast, Mr. Major met with security chiefs, Belfast's lord mayor, the Unionist politician Nigel Dodds and the economy minister, Richard Needham.
Mr. Needham has been the official called on most frequently to formally respond to IRA attacks, since most of the bombing of central Belfast over the past two months was evidently designed to retard the city's economic resurgence.
The government has promised to rebuild the damaged city center.