A man believed to be strapped with explosives has taken nine adults and two children hostage in a post office in the Ukrainian city of Kharkiv, police said on Saturday.
The unidentified man is calm, has not made any demands and is in regular contact with police via the telephones of the hostages, regional police chief Oleg Bekh told 112 news channel.
Television footage showed police and parked police cars outside a two story white-and-yellow building in the northeastern city. The area has been closed off to traffic.
"We are trying to do everything to maintain communication with him and to do everything that is necessary to ensure the people are released," Bekh said.
The man in the post office was concerned about the recent prisoner exchange between the Ukrainian authorities and pro-Russian separatists and thought more prisoners should have been released, Bekh said, adding police did not know what he wanted.
Ukraine and the separatists swapped hundreds of prisoners on Wednesday in the biggest such exchange since the outbreak of a conflict in the eastern Donbass region that has killed more than 10,000 people.
Efimov confessed his intention to carry out an attack with explosives against the aforementioned cathedral on Sunday, for which he prepared an explosive. The prosecution ordered the preventive detention of the suspect until next February 13.
During the interrogations, the arrested man was repentant and willing to offer information about his accomplices and indicated that his actions were influenced by other people.
Efimov leased a metal container in Litovski Street 8A and in the chemical store, whose strong smell caught the owner's attention, who opened it with a duplicate and found there a white powder, which later turned out to be explosive, knobs of acetone and plastic gloves.
The next day, the owner of the container observed by a closed-circuit camera how Efimov left there materials in several construction bags. In one of them, the owner of the container found a coffee can full of nails and explosive substance.
In general, terrorists stuff their homemade bombs with screws, small sheets of metal, pellets or nails to increase their deadly effect.
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