MOSCOW, August 21 (RIA Novosti) - A turf war between commercial groups is at the center of an investigation into a bombing Monday morning at a popular Moscow market that left at least eight people dead, Moscow's prosecutor said.

Yury Syomin said investigators were also considering terrorism in the attack, which he said also left 41 in the hospital. He gave no further information on the fatalities at Cherkizovsky market in the northeast of the city.

With uncertainty about the force of the explosion - a source in the investigative group suggested it was the equivalent of 200-500 grams of TNT, whereas prosecutors later said it could have been as much as one and half kilograms (3.3lb) - Syomin said the bomb was the equivalent of 1kg (2.2lb) of TNT.

"An explosive device consisting of 1kg of TNT without any solid encasement exploded," he said. "The explosion occurred between two rows of metal containers. There was also a cafe nearby. Only a small area was affected."

One witness said he had seen a bag being brought to the scene before the explosion.

"We saw three people leave a bag at the market's cafe," he said. "Knowing security measures, especially with regard to unattended items, two market employees ran after the people who left the suspicious bag. At precisely that moment it exploded."

Syomin said the explosive device, which went off at 10:27 a.m. Moscow time (6:27 a.m. GMT), had probably caused a liquefied gas cylinder to detonate. Two bangs were heard, although police earlier said there had only been one explosion.

Investigators said they had almost finished questioning market workers and had a description of the suspects, which would be used to compose an identikit.

Syomin said no information was available yet about those killed, including their ethnic backgrounds.

Like most markets in Moscow, many traders are from the North Caucasus region and former southern Soviet republics. Prosecutors initially investigated a turf war as being behind a September 2000 bombing that killed 13 in an underpass in the heart of Moscow, although the mayor suggested the "Chechen trace" could also be seen in the incident.