Police have searched for explosives in apartment buildings throughout the Russian capital, and have demanded identity documents from people in subway stations, outdoor markets and busy intersections throughout the city.
Russian authorities suspect Islamic militants from southern Russia are responsible for three huge explosions this month that have killed at least 275 people, including 118 who died in a Moscow apartment explosion on Monday.
No one has claimed responsibility for the explosions, and authorities have not produced any evidence linking the blasts to any particular group.
Still, police have concentrated mostly on dark-skinned men assumed to be from the southern Caucasus Mountains region, where Islamic rebels are battling government troops.
The Interfax news agency, citing law enforcement sources, said authorities have found a truck that may have been involved in bringing explosives to Moscow. Police suspect that explosives may have been transported to the capital hidden in bags labeled as sugar.
But there was no word on whether police had been able to link the truck and its contents to the two Moscow explosions in the past week.
Police said Tuesday that three suspects had been detained. Two of the detainees owned companies with offices on the ground floor of one of the destroyed buildings.
Police released sketches and photographs of three other men suspected of involvement, including a man who allegedly rented space in both buildings.
Prime Minister Vladimir Putin said Wednesday that the people who carried out the bombing were hiding in the breakaway republic of Chechnya, adding that Russia would ask the Chechen government to Â"hand over the criminals.Â"
On Tuesday, Putin called for a Â"quarantineÂ" around Chechnya to cut off a route for weapons and Islamic militants, and for applying Â"tough economic sanctionsÂ" against the territory.
Meanwhile, President Boris Yeltsin's government has said it has no intention of imposing emergency regulations.
Gennady Seleznyov, the speaker of parliament's lower house and a frequent critic of Yeltsin, also said he was opposed to a state of emergency.
Russia has Â"enough strength and the means to do away with the rebels in (southern Russia) and with the terrorists in the rest of Russia,Â" said Seleznyov, a Communist.
The government has Â"all the necessary legal levers to restore order even in this serious situation,Â" Seleznyov said.
Russia has not faced terrorism on this scale previously, and the government has asked for the United States and other countries to provide expertise.
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