* Bombing in west second on military since April
* Al Qaeda north Africa branch still active
* Algerian officials worried about Libyan spillover (Adds analyst comment)
By Hamid Ould Ahmed
ALGIERS, July 13 (Reuters) - A roadside bomb killed seven members of Algeria's security forces as they were patrolling in the west of the country, the second major attack on the military in three months.
Militants attacked a military convoy in Sidi Bel Abbes province in western Algeria late on Saturday, the defence ministry said in a statement. Three soldiers and four municipal guards were killed in the blast.
The statement said "terrorists" carried out the attack, a term used by the authorities to refer to Islamist militants.
Violence and militant attacks have become rarer since Algeria ended its decade-long 1990s war with armed Islamists, but the north African branch of al Qaeda and other militants are still active, especially in the south where desert borders are porous.
Al Qaeda in the Islamic Maghreb, as the regional al Qaeda branch is known, also carries out sporadic attacks in the north. It killed at least 14 soldiers in an ambush in April in mountains east of the capital Algiers.
"They want to say: 'We are still here,'" said local newspaper editor and security expert Mounir Boudjema. "It was not a large attack because it is easy to bury a bomb and let it explode when a convoy passes by."
The municipal guards, whose members were among those killed in Saturday's attack, are part of a security body set up by the interior ministry in the 1990s to help fight Islamist militancy.
Algerian officials are concerned about spillover from the turmoil in neighbouring Libya, where fighters linked to al Qaeda take refuge in the southern deserts.
Militants crossed over the border from Libya to carry out the worst attack in Algeria in years in January 2013 when fighters raided the In Amenas gas plant, in a siege that killed 40 oil workers, most of them foreigners. (Editing by Patrick Markey and Susan Fenton)