BONN, West Germany (AP) _ A roadside bomb blast triggered by a beam of light injured a senior West German official today, and the Red Army Faction terrorist group claimed responsibility.

Hans Neusel, the state secretary of the Interior Ministry, escaped with only minor injuries, though his car was wrecked.

Neusel, whose ministry is in charge of law enforcement, was taken to the hospital but released a short time later and returned to the scene of the bombing, a highway on the outskirts of Bonn.

He later told reporters he was happy to be alive.

Today's bombing was the first Red Army Faction attack since eight long- sought fugitives - reputed to be top members of the group - were captured in East Germany in recent weeks.

The Red Army Faction has been responsible for a series of killings and bomb attacks in West Germany in the last two decades.

The eight reputed members of the group captured in East Germany had been living there under assumed names, some for as long as 10 years. Some say they had been granted sanctuary by East Germany's former Communist government.

West German officials had believed the roundup had put a serious dent in the group's ability to carry out attacks.

Today's explosion demolished Neusel's silver BMW sedan, shattering the windows, ripping apart the interior, smashing its doors and tearing open the hood and the trunk lid. The blast blew a large hole in the highway and damaged the guardrail.

Officials said Neusel probably escaped serious injury because he was driving, and the bomb went off on the car's passenger side. He suffered only minor cuts.

The Interior Ministry said the 62-year-old official had no security detail, and his automobile was not equipped with any protective equipment such as armor plating or bulletproof glass. West German television said Neusel's driver was on vacation.

Police said a letter claiming responsibility in the name of the Red Army Faction was found near the site of the attack and that it appeared to be genuine.

Hans-Juergen Foerster, spokesman for the federal prosecutor's office, said the letter carried the Red Army Faction symbol, a red star superimposed by a machine gun. It said the attack was carried out by the ''Jose Manuel Sevillano commando.'' Foerster said Sevillano was a convicted member of the Spanish terrorist group GRAPO who died in May after a six-month hunger strike.

Foerster said the bomb was triggered by the car crossing a light beam. He said the devise used today was the same as the one used in a bomb attack that killed Siemens manager Karl Heinz Beckurts in July 1986 near Munich.

The attack also resembled the November killing of Deutsche Bank chief Alfred Herrhausen, whose car was blown up by a bomb planted by the Red Army Faction near Frankfurt, he said.

The most recent previous terrorist attack on a government official came in September 1988, when shots were fired at Hans Tietmeyer, a state secretary in the Finance Ministry. Authorities said Tietmeyer apparently had been the target of a kidnapping attempt.

Neusel later spoke with reporters about the attack, telling them: ''You can understand that I am especially happy to be able to be with you today.''

Speaking in a calm, unemotional voice, described the impact of the bomb blast, saying, ''Naturally the sensation of shock was there.''

He said he believed the bombers must have had an observation post near the site of the attack, but told authorities earlier he saw no attackers.

Neusel called on the Red Army Faction to cease its long campaign of terror.

''I appeal emphatically for you to give this up,'' he said. ''Even if you were successful, how would that have changed the fact that we are a free democracy?''

The federal prosecutor's office in Karlsruhe, which is in charge of investigating terrorist attacks, took over the investigation.

Neusel, the No. 2 official at the Interior Ministry, is in charge of domestic security and police affairs.