Libyan leader Muammar Gaddafi was in the house bombed by NATO war planes but he and his wife escaped unhurt even as his youngest son and three grand children died.

The attack took place on Saturday evening and was targeted at Gaddafi. The leader and his wife were in their son Saif al-Arab's house at the time of the attack, the Libyan government spokesman Moussa Ibrahim said on Sunday. The spokesman said both escaped unhurt, adding that the deaths would be avenged.

The killed son was not a key member of the Gaddafi apparatchik. The 29-year old was a student in Germany, according to reports. Gaddafi has another son named Saif -- Saif al-Islam -- who is one of the most prominent leaders in the country after Gaddafi.

The attacked house stood in a residential area of Tripoli.

NATO acknowledged the attack and said it regretted the loss of life. We regret all loss of life, especially the innocent civilians being harmed as a result of this ongoing conflict, NATO commander Lt. Gen. Charles Bouchard said.

NATO is fulfilling its U.N. mandate to stop and prevent attacks against civilians with precision and care -- unlike Gadhafi's forces, which are causing so much suffering, he said.