Cairo - The Egyptian air force has destroyed 15 vehicles carrying weapons and ammunition after they illegally crossed into the country from Libya, a military official said on Monday.In a separate announcement, Egypt said its security forces had killed eight militants who were being trained to attack government and Christian targets, in a shootout in the country's southern desert.Army spokesman Colonel Tamer al-Rifai said the armed forces had received "intelligence on a large number of vehicles gathered on the Western border readying to infiltrate" Egypt."Our planes took off to survey the area and went into action as soon as the vehicles breached the border," he said in a statement on Facebook."The operation lasted 48 hours with surveillance and air strikes. Five four-wheel-drive vehicles carrying weapons, ammunition and smuggled goods were destroyed," he said, without mentioning any casualties.A military official, who spoke to AFP on condition of anonymity, said the vehicles came from chaos-wracked Libya, where rival militias are battling for control and the Islamic State group has a presence.In the shootout in the south of the country, those killed included Helmi Masri Mohareb, a leader who transported militants across Egypt's southern border to join training camps, the interior ministry said in a statement.The statement did not say when or exactly where in the desert they were killed, nor in which country they were alleged to have received training.The security forces came under heavy fire as they pursued the militants, before shooting back at them, the ministry said.'State of chaos' "This led to the deaths of the mentioned leader and seven of the terrorist elements," of whom two had been identified as Muslim Brotherhood members wanted in other cases, it said.The statement did not say whether there were any casualties among the security forces.Mohareb is also wanted in several cases, and has received the death penalty pending the approval of the mufti, Egypt's official interpreter of Islamic law, though his opinion is not legally binding.According to the statement, these groups were formed according to "assignments issued by the (Muslim Brotherhood) organisation's leadership abroad to its leadership in the country."They planned "to form groups to carry out a series of hostile operations in the coming period by sending elements from these groups to join training camps abroad."They were then to "return to target state institutions, and government and Christian buildings, and a number of public figures and policemen, with the aim to create a state of chaos, instability, and to foment internal strife."The Brotherhood, once Egypt's largest opposition movement, has long denied involvement in violence.The Brotherhood's Mohamed Morsi was elected as Egypt's first civilian president in 2012, but the army overthrew him a year later following mass protests against the divisive Islamist's rule.Since then, an extensive crackdown on the group has left it in disarray with competing wings that have disagreed on whether to use violence, after police quashed their protests.Analysts say a section of the Brotherhood has encouraged armed attacks against policemen in Egypt.