British Prime Minister Margaret Thatcher escaped unhurt here today after a huge early morning explosion, apparently caused by a bomb, ripped through the hotel where she was staying at the Conservative Party's annual convention.

The blast blew a huge hole in the top three floors of the Grand Hotel and blew debris, glass and furnishings into the street and onto the promenade along the beach at this south coast resort where the Conservatives are meeting. Police quickly cordoned off the area.

Thatcher emerged safe but shaken and was taken along with the foreign secretary and home secretary to the Brighton police station. At least 30 persons were reported injured, and rescue workers continued to sift through the debris. According to one unconfirmed report, two persons were killed.

Damage to the bathroom of Thatcher's suite and the sitting room of Foreign Secretary Geoffrey Howe's quarters was said to be extensive.

Thatcher later was taken to an undisclosed location, but she told reporters that she was okay, the conference would go on, and that she would make her closing speech as scheduled today.

Immediately after the blast, according to eyewitnesses, hundreds of guests began staggering out of the hotel. Dozens of ambulances were brought to the hotel. Police began evacuating other nearby buildings, because there were indications that other unidentified packages have been found.

There was no official confirmation that the blast was caused by a bomb, but police said that was a major suspicion.

Eyewitnesses said the explosion took place at about 3:05 a.m. The stately old seaside hotel is headquarters for the Conservatives at their annual convention, and it was jammed with hundreds of party officials and delegates.

The blast blew a gap that appeared to be about six feet wide and perhaps 10 feet or more deep and extended upward from the fourth floor of the hotel through the roof three stories above.

Security around the convention hall next to the hotel was fairly tight during the day, with police inspecting any packages or briefcases taken into the convention.

However, while police were also around the Grand Hotel, they were not inspecting packages or briefcases of those entering that building during the three days of the Conservative Party meeting here. Police had been advising those at the conference not to wear their credential badges outside the hall, apparently out of concern that one might fall into unauthorized hands.

Yesterday, expressions of grave concern about record unemployment had broken through the customary calm of the ruling Conservative Party convention, with some delegates warning of serious political risks if the government failed to deal more effectively with the problem.

"We have overrun the point where we can remain silent," Tory trade unionist Ivor Humphrey told the convention.

With Thatcher looking on, Humphrey said, "We have been told there is no alternative" to tough economic policies. But, he said, "there has to be an alternative. Otherwise one day you will experience an explosion the likes of which you've never seen before."

The convention overwhelmingly approved a resolution stating that while the government had made a "positive contribution to assist the unemployed, there is still a gap between help available and the needs of unemployed."

To a number of delegates here, however, that resolution was a considerable understatement. Several commented privately that they were worried that not enough was being done or that the government, with its big majority in Parliament, was too complacent.

Despite forecasts before the 1983 general election by Chancellor of the Exchequer Nigel Lawson that unemployment would fall this year, it has risen steadily, reaching an all-time high of 3.28 million, or 13.6 percent of the work force, last month.

The archbishop of Canterbury recently has criticized the results of Thatcher's economic approach. Public opinion polls that show Thatcher with a clear lead over her Labor Party rival also show that nine out of 10 voters think she is not doing a good job handling unemployment.

But in speeches here today by Employment Minister Tom King and yesterday by Lawson, the government insisted that there was "no shortcut," as Lawson said, to reducing unemployment.

Britain's problem was made more difficult by a steadily increasing work force that added 160,000 more people this year, he said.

King promised to double the number of people in adult-training programs next year. That was the only new initiative in either his or Lawson's presentations here, and it seemed to disappoint many delegates as too little.

Lawson, in particular, sought to blame what he called "monopolistic trade unions" for wage demands "that price men out of work."

Ministers and delegates here have invoked the creation of 15 million new jobs in the United States during the past decade to verify the benefits of what Lawson called "the free-enterprise culture of lower taxes, less government spending, less red tape . . . and no socialist party."