Moscow, Russia - The death toll from the attack on a Moscow concert hall claimed by Islamic extremists rose on Wednesday to 143, Russian authorities said.

Authorities listed the names of the dead on the Russian Ministry for Civil Defense and Emergency Situations five days after last Friday's attack, the deadliest claimed to date by Islamic State on European soil and the worst in Russia in two decades.

By Wednesday afternoon, 80 people injured in the attack, including six children, remained in hospital, TASS news agency quoted Russian Health Minister Mikhail Murashko as saying.

An anonymous medical source told TASS that 205 people had received outpatient care.

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Russian Deputy Prime Minister Tatiana Golikova told reporters the previous day that many people in shock had initially not returned to the hospital for treatment.

On Friday, gunmen opened fire at the Crocus City concert hall near Moscow, also setting fire to the venue.

Four attack suspects – all from Tajikistan, according to Russian state media – are under arrest along with several suspected accomplices. A Moscow court has ordered the men be held in pre-trial detention until May 22 – a date likely to be extended until a full trial.

Russia said Saturday it had arrested 11 people in connection with the attack. There has been no information on the other seven.

The attack was swiftly claimed by Islamic State, although Moscow has repeated its initial line of a link to Ukraine. Kyiv rejects any involvement.

Russia has for some years been a target of Islamic State owing to its role in suppressing unrest in regions with a substantial Muslim majority as well as its support for the regime in Syria's civil war.

On Monday, three days after the attack, President Vladimir Putin admitted for the first time that the presumed gunmen were radical Islamists but continued to insist on a link to Ukraine, saying the perpetrators were headed there when they were caught some 93 miles from the border.