ROSTOV-ON-DON, May 14 (RIA Novosti) - A couple and their landlady have been killed in a special operation in Nazran, the largest city in Russia's North Caucasus Republic of Ingushetia, local prosecutors said on Wednesday.

On Tuesday police cordoned off a house in Nazran, following reports that a militant, wanted for a number of serious crimes, and his wife had been renting a basement there.

The militants refused to surrender and shot their landlady before being killed when police returned fire.

An assault rifle, a gun and a grenade were discovered at the scene. An investigation is underway.

In a separate development, an arms cache, containing an automatic weapon, three Kalashnikov assault rifles, a grenade launcher round and 865 cartridges, was found in a forest near the town of Karabulak, northeast of Nazran, a police source said.