A powerful bomb damaged a suburban IBM office building tonight, just four hours after a bomb caused extensive damage to a South African transport office on Long Island.

An anonymous caller told an editor at the Gannett Westchester Rockland newspapers in White Plains that the IBM explosion at Harrison, N.Y., was related to the earlier blast at the South African facility at Elmont in Nassau County.

No injuries were reported in either case.

The anonymous caller who warned of the explosion gave no indication what, if any, group instigated the bombings.

Randall Robinson, executive director of TransAfrica, a Washington-based lobby on African and Caribbean issues, said tonight he "did not have a clue" about who might have been responsible. But he added, "I'm not at all surprised because a number of groups in this country are enormously angry at South African practices and at the extent to which the United States has opened its arms to South Africa and South African entities here."

IBM, which has extensive operations in South Africa, has been a leading target of groups critical of U.S. investments in South Africa. However, despite protests at stockholders meetings, there has been no act of violence against IBM comparable to tonight's bombing.

Rich Leonard, night metro editor of the White Plains newspaper, said a caller said everyone should be evacuated from the IBM building because a "huge bomb" would go off in 30 minutes. He recalled the person saying, "We did South African Airways."

The call was repeated within five minutes, and the bomb exploded at 7:40 p.m., Leonard said.

Damage to the IBM building was "very bad," according to Harrison police. But by the time it occurred, everyone had been evacuated, they added.

The damaged building, one of 27 IBM facilities in Westchester County, is a sales and service branch office where some 550 persons usually work. Only about 30 were there when the bomb warning was given shortly after 7 p.m., however.

The earlier Long Island blast took place at the South African Railways Procurement Office in Elmont, N.Y., according to United Press International. Nassau County police said that bomb went off only minutes after the four-story building was evacuated and after a bomb squad threw a blast blanket over the device.

"They just about got away," said Sgt. Michael Ford of the bomb squad. "Another few minutes--they would have been blown away."

The blast "blew the bomb blanket to smithereens," he added. The blankets are designed to contain explosions.

Some 70 to 100 people were evacuated from the building, which also houses other offices, police said.