A train carrying explosives collided with a coal train in the Russian Republic, setting off an explosion and fire that killed four people and injured 280, Soviet media said.

Twelve dwellings were destroyed, and hundreds of people were left homeless after Monday's blast, the government newspaper Izvestia said.Izvestia said the explosion in a switching yard near the Ural Mountain city of Sverdlovsk sent a column of black smoke and red flames into the sky and created a crater 180 feet wide and 30 feet deep.

It did not identify the explosives contained in two cars of the freight train, but said they were for use in the domestic economy.

Izvestia said two workers died at the scene and two other people died later at a hospital. It reported 87 people were hospitalized. The official Soviet news agency Tass said 280 people sought medical help.

The collision in Sverdlovsk, an industrial city about 850 miles east of Moscow, was the third major rail accident in the Soviet Union within six months. On Aug. 17, a passenger train crashed on its way from Leningrad to Moscow, killing 24 people and injuring more than 100. In June, three cars loaded with explosives blew up in the city of Arzamas, about 240 miles east of Moscow. Eighty people died and 229 were injured.

Monday's explosion caused tanks of oil and gas to catch fire, Izvestia said. "Dark smoke covered the entire city," it said.