Tripoli, Libya (CNN) -- Libyan leader Moammar Gadhafi's youngest son -- Saif al-Arab Gadhafi --was killed after a NATO airstrike, a spokesman for Libya's government said Sunday at a press conference.
Moammar Gadhafi and his wife were in their son's house when it was targeted, spokesman Musa Ibrahim said. Both of them are in good health, according to the spokesman.
The victim is one of two of Gadhafi's sons named Saif. The other is Saif al-Islam Gadhafi, who had previously touted reform but has emerged as one of his father's most visible defenders in recent months.
Ibrahim said several of Moammar Gadhafi's grandchildren also died in the attack.
The house in Tripoli was destroyed by the strike, with a massive crater where the house used to be. At least one unexploded bomb could be seen at the scene.
The building was in a residential area of Tripoli, according to Ibrahim, who insisted that Saif al-Arab Gadhafi was a student in Germany who was not deeply involved in Libya's military and government. The 29-year-old was one of Gadhafi's eight biological children.
Ibrahim railed against NATO after the fatal strike, calling it an illegal act and a "war crime."
NATO officials could not immediately be reached for comment.
A spokesman for the Libyan opposition doubted the veracity of the report, saying, "In all honesty, we never heard of Saif al-Arab until the start of the uprising."
"We don't believe this is true," said Abdul Hafiz Ghoga, deputy chairman of the Transitional National Council in Benghazi. "It is all fabrications by the regime in a desparate attempt to get sympathy ... This regime constantly lies and keeps lying."
Ibrahim, the spokesman for Gadhafi's government, accused NATO of launching the strike in order specifically to kill the Libyan leader.
Earlier this week, U.S. Ambassador to Libya Gene Cretz acknowledged that "our own laws" would affect any decision to try to assassinate Moammar Gadhafi directly.
"I don't believe that any credible group or individual sees the solution to the Libyan problem without the removal of Moammar Gadhafi, one way or the other," he said. "But our job and our goal is to get a political solution, but through the means that we are allowed to by our own laws."
This is not the first time that Moammar Gadhafi reportedly has been at the site of an airstrike that killed one of his children.
In April 1986, U.S. forces launched an airstrike that targeted Moammar Gadhafi's residential compound. As a result, the Libyan leader's adopted daughter, Hanna Gadhafi, was killed.
At the time, President Ronald Reagan told the American people the bombings were an act of self-defense following the bombing of a West Berlin club that killed two American servicemen and injured several others.
And on Monday, Ibrahim issued a defiant statement saying Moammar Gadhafi was alive despite what the Libyan government called a NATO attempt to kill him by bombing his compound.
"The message that was sent by NATO in the early hours of this morning was sent to the wrong address," Ibrahim said.