CAIRO (Reuters) - The Egyptian military said on Monday its air force hit eight four-wheel-drive vehicles carrying arms and explosives at Egypt s western border with Libya, killing the militants on board. A military statement gave no details of the number of fatalities or about which militant group it suspected was transporting the arms. Last Friday Egypt s security forces suffered one of their deadliest attacks, when militants killed police officers using rockets and explosives in a remote area about 135 km (85 miles) southwest of Cairo.    Egyptian security forces have been battling an insurgency by Islamic State that was largely concentrated in the Sinai Peninsula but has in recent months extended to other parts of the country. Egypt has carried out air strikes in Libya occasionally since its neighbor descended into factional fighting in the years following the 2011 civil war that ousted Muammar Gaddafi. In a separate statement, Egypt s armed forces said they had  raided a terrorist stronghold in northern Sinai, killing six very dangerous takfiris  - a term used by hardline Muslims to accuse other Muslims of apostasy.  The statement added that in the raid, which was carried out after the military received information of the stronghold, security forces confiscated  a large amount of arms and ammunition.   