Vladikavkaz (Russia), Sep 1 (RIA Novosti) Around 3,000 police officers are guarding schools in the south Russian republic of North Ossetia Tuesday, as locals mourn the victims of Beslan school massacre five years ago.

The interior ministry said police will remain at the schools for three days, guarding round the clock.

Terrorists attacked Beslan's school No.1 Sep 1, 2004, when parents, teachers and pupils were gathered for the first day of term.

The school was held in a three-day siege in which at least 334 people were killed, including 186 children.

On Tuesday morning, over 2,500 people gathered outside the school for a memorial service, police said.

Officials laid flowers in the sports hall, where the hostages were held, and tributes were read out in memory of the victims.

A cross has been placed in the middle of the hall, and mourning wreaths and photographs of those killed in the massacre line the walls.

Last week, Russian Interior Minister Rashid Nurgaliyev ordered heightened security at schools in the region, in the run-up to the Beslan anniversary, and in view of the recent surge in militant violence in the North Caucasus.