CAIRO (AP) — Egypt’s military says 21 troops are dead after gunmen armed with rocket-propelled grenades attacked a border guard post in the western desert near Libya today.

A military spokesman says one of the rockets struck a cache of weapons at the checkpoint, sparking an explosion. Egyptian forces later seized two car bombs before they exploded.

Another military official says about 20 gunmen in vehicles mounted with weapons took the checkpoint by surprise. The official says three of the attackers were killed in the battle.

The state news agency MENA says it’s the second time this border patrol company has come under attack in the last few months. The earlier attack killed six troops.

Egypt has vowed to tighten security along its long, porous borders with Sudan and Libya, which are often crossed by arms smugglers. Egypt has been flooded with weapons, mostly from Libya, following the 2011 civil war that toppled longtime dictator Moammar Gadhafi.

Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.