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

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

Terrorists attacked Belsan's school No. 1 on September 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, local police said. Regional 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. He also voiced concern over the lack of security guards at most Russian schools.

The North Ossetian interior ministry said that for the anniversary, all local schools have been provided with three to seven police officers on constant guard, and that extra traffic police have been deployed on roads leading to schools. The town of Beslan will be policed by 400 officers up to September 3. Russian Interior Ministry troops and special forces have also been sent to the region.

On Tuesday morning alone, Russia's North Caucasus was hit by at least three terrorist attacks - two car bombings in Dagestan, in which one person died and at least 19 were injured, and one roadside bomb blast in Chechnya, in which three soldiers were injured. A gas pipe blast in Ingushetia is being considered as a possible terrorist attack.