Soldiers and civilians in southern Russia observed a day of mourning Monday for the victims of a suicide truck-attack that killed 50 people at a military hospital.

Officials dedicated a memorial stone at the ruins of the hospital, destroyed Friday when a truck packed with explosives crashed through its gates and blew up in a giant fireball. Many of the dead were soldiers wounded in the war in nearby Chechnya (search).

Flags flew at half-staff over all government buildings in the regional capital Vladikavkaz (search). Workers began their day by observing a moment of silence for the victims of the attack. Military units throughout the region held similar ceremonies.

Security was tightened throughout the region, with police patrolling other potential targets. Troops sealed off the main military hospital in Vladikavkaz, barring all nonmilitary visitors from the building.

Funerals for the victims began Sunday and were to continue Monday. Sixty-four victims remained hospitalized, many in serious condition, officials said Sunday.

The attack on the hospital was the latest in a series of suicide bombings in and around Chechnya and in Moscow that have killed more than 150 people since May, shattering the Kremlin's claims that a nearly four-year war in the republic is winding down.

President Vladimir Putin has vowed that the latest terrorist attacks will not stop efforts to restore "normal peaceful life" in the region.

In a meeting with officials late Sunday, Putin castigated authorities for what he said was negligence. "

The laxity that we have seen in a series of cases, and which is conducive to crimes and terrorist acts, has gone beyond all bounds," he said.

On Sunday, military officials announced heightened security measures in the region. Large trucks will be barred from military communities and the grounds of military hospitals and clinics.

Parking lots will be moved at least yards from buildings and other areas where people gather at military bases in the district, officials said.

Russian forces withdrew from Chechnya following a 1994-1996 war that left separatists in charge. The Russians returned in 1999 after incursions into an adjacent region and apartment-house bombings in Russian cities that killed some 300 people.

Defense Minister Sergei Ivanov (search) said Saturday that the explosives used Friday resembled those used in the apartment-house bombings.