State television, citing an army statement, reported that Egyptian warplanes carried out at least six airstrikes against "terror camps" in the eastern Libyan city of Derna.
It added that the aerial raids had been carried out after making sure that men from those camps were involved in the bus attack.
"Egypt will not hesitate in striking any camps that harbor or train terrorist elements whether inside Egypt or outside Egypt," said Egyptian President Abdel Fattah el-Sisi on Friday evening in a televised speech hours after the terrorist attack in the country's Minya province.
Sisi went on to say that an airstrike against the camps was being conducted as he spoke, adding that the carnage would not be left unanswered.
According to a statement by the Egyptian Interior Ministry, masked assailants in three pickups stopped the vehicle and opened fire on it as it was heading for the Saint Samuel monastery in the province, over 200 kilometers from Cairo. The attack also injured more than two dozen other passengers. A number of children were among the dead.
There was no immediate claim of responsibility for the Friday morning attack.