BESLAN, Russia (CNN) -- Hundreds of people held hostage at a school in southern Russia fled to safety Friday, but scores are reported dead as pitched battles continue between troops and hostage-takers.

Reports said the hostages may have numbered as many as 1,200 and that 70 percent of them were children.

It was not clear whether several children and others, who were being held by a remnant of the hostage-taker hours after the school was stormed, were still in captivity.

Valery Andreyev, head of the local branch of the FSB intelligence service, said 20 hostage-takers had been killed, 10 of them from Arab countries, after Russian troops stormed the school earlier Friday.

Until now, the rebels have been regarded as residents of the restive republic of Chechnya or other Caucasus areas.

Many fatalities have been reported. Around 100 people have been seen dead in the school gym by journalists.

There also was a report that 23 bodies, including 17 children, were outside a hospital morgue and 10 more bodies were inside. One news report said the death toll could exceed 200.

Near the scene, news footage showed dead bodies of children on stretchers.

One woman leaned down to a young boy, hugging and caressing the youth, who shared a stretcher with another body. Other women stood shocked, holding their hands to their mouths and weeping.

Andreyev said 400 people had been freed in the storming operation, with many of them wounded. Earlier, scores of survivors ran from the school and people were being carried on stretchers to ambulances.

Special forces were mopping up pockets of rebel resistance at the school, clearing the burned-out building of wounded hostages and hunting down the hostage-takers who fled after special forces stormed the site.

Russian forces say they are in control of the school building, but the gunfire continued into the late afternoon and there were reports of militants firing from another structure in the school compound.

Hostage-takers have grenade launchers, small arms and have been sniping, and troops and the abductors have been fighting pitched battles.

The hostage incident began two days ago when an armed gang of Chechen rebels took hundreds of children, parents and teachers hostage on the first day of school in Beslan, located in North Ossetia, near Chechnya, where rebels have been fighting Russia and demanding independence for that small republic.

The storming was not planned, Russia said.

A local official from Russia's FSB intelligence service told Russian media the troops had been ready for a long siege.

However, the forces stormed the building around midday after Russian officials, under a cease-fire agreement with militants, tried to collect bodies lying outside the building.

There was an explosion, hostages fled, and hostage-takers opened fire on the children and rescue workers. One of the workers was killed and another was wounded.

Russian troops then opened fire at the rebels, and the battle began.

Several hours later the scene remained in chaos, with pockets of resistance remaining and machine-gun fire heard on the scene and troops going room-by-room as the wounded were being taken out of the building.

It is thought that the people in the gym might have died when explosives triggered the collapse of the roof and a fire.

Russian forces blasted holes in a building of the school to create exit points. A Russian soldier was hit by a bullet, and a news cameraman was hit.

The explosions heard at the scene could have resulted from mines and booby-traps planted near the school by militants, one report said.

Interfax quoted a Defense official as saying that "the terrorists planted a lot of mines and booby-traps filled with metal bolts in the gym" where hostages were held.

Officials said the hostage-takers had been holding more than 350 children, parents and teachers. Relatives said the number was much higher -- about 1,000.

Children who survived said they were denied food and water and had to take off their clothes because of heat. Some boys said that because they lacked liquids, they had to drink their own urine.

The standoff followed a bloody week in Russia, in which a female suicide bomber Tuesday killed nine people outside a Moscow subway station and two airliners were downed by two suspected Chechen female suicide bombers on August 24, killing all 89 people aboard the planes.

Russian officials have said the new wave of attacks is an attempt at revenge for last weekend's elections in Chechnya in which a Kremlin-backed candidate won the presidency.