Updated

Rescuers stopped searching for victims of a truck-bombing at a military hospital as relatives held the first funerals Sunday for the 50 people killed in Friday's blast, the latest in a series of homicide attacks.

Meanwhile, President Vladimir Putin (search) lashed out at the "laxity" he said has aided attackers in recent months.

Authorities expanded security measures across the southern region of the country to prevent a repeat of Friday's assault in Mozdok (search), a major staging point for Russia's second military campaign against Chechen rebels in a decade.

Overnight, rescuers with sniffer dogs pulled the body of a surgical nurse and at least four others from the rubble of the four-story brick building, bringing the death toll to 50 before the search was called off, said Lt. Col. Yuri Miroshnichenko, spokesman for the Emergency Situations Ministry in southern Russia. Sixty-four victims remained hospitalized, he said.

At the site of the blast, soldiers erected a small black marble memorial stone and a tall wooden cross.

A truck packed with explosives crashed through the hospital gates Friday night. Authorities have said they believe one homicide attacker was in the Kamaz truck, which they said had been bought and sold several times in recent weeks.

Two people who sold the truck have been detained as suspects, the Interfax news agency quoted Deputy Prosecutor General Sergei Fridinsky as saying. He said authorities hope the detainees will lead them to "other participants in the crime" and that investigators are focusing on Chechnya, North Ossetia — where the attack took place — and nearby regions.

Citing unidentified law enforcement sources in North Ossetia, Interfax reported that authorities suspect that Chechen rebel warlord Shamil Basayev was behind the attack. A Web site that has conveyed purported claims of responsibility by Basayev for past attacks has been inaccessible, and prosecutors could not be reached to comment on the report.

Wooden coffins decorated with dark-green wreaths arrived in Mozdok by plane. Many of the dead, mostly military personnel, residents and hospital workers, were to be buried Monday, which was pronounced an official day of mourning throughout Russia's North Caucasus Military District (search).

But funerals for a hospital security guard — who played soccer on a local team — and the chief of the surgery department were held Sunday, according to televised reports.

Weeping mothers gathered outside a hospital in the region, waiting for information. No official list of the injured was posted; instead relatives were urged to call information hot lines. Meanwhile, authorities began the process of handing out compensation to victims and their relatives.

Homicide bombings in and around Chechnya (search) and in Moscow have killed more than 150 people since May. Friday's blast also was the third devastating truck-bomb attack in southern Russia since last December, when the headquarters of the Moscow-backed administration in Chechnya was heavily damaged in an attack that killed 72 people.

Putin, in a late Sunday meeting with Prosecutor General Vladimir Ustinov and Supreme Court chairman Vyacheslav Lebedev, demanded that authorities do more to prevent such attacks.

"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," Interfax and state-run Rossiya television quoted Putin as saying.

"One develops the impression that the state somehow does not react or is not in condition to react to such events."

Putin, who gained popularity partly because of his tough stance on Chechnya, has been unable to fulfill promises to crush resistance and bring peace to the region.

On Sunday, military officials announced heightened security measures throughout the military district, which encompasses Chechnya and much of southwestern Russia.

Large trucks will be barred from military communities and the grounds of military hospitals and clinics, Interfax quoted Col. Igor Konoshenkov, an aide to the district commander, as saying.

Parking lots will be moved at least 100 yards from buildings and other areas where people gather at military bases and units in the district, Konoshenkov said. Security also was stepped up at fuel storage areas, weapons and ammunition dumps and living quarters of military personnel.

Russian authorities have been at pains to show that stability is returning to Chechnya and the surrounding provinces, which have been targeted by rebels in years of war and chaos. Putin has vowed that terrorist acts will not stop efforts to restore "normal peaceful life" in the region.

Russian forces withdrew from Chechnya following a 1994-1996 war that left separatists in charge. They returned in 1999 after incursions into an adjacent region and apartment-building bombings in Russian cities that that killed some 300 people. Defense Minister Sergei Ivanov (search) said the explosives used Friday resembled those used in the apartment-house bombings.

The Kremlin refuses to negotiate with rebels and has taken steps its says are designed to bring peace to Chechnya, including a regional presidential election scheduled for Oct. 5.

Critics have questioned how fair elections can be held in conditions of war and have suggested that the vote is an attempt to legitimize Moscow-backed administration chief Akhmad Kadyrov's control over the region. On Sunday, Kadyrov formally announced his intention run in the election.