British police arrested three more people Wednesday in south Manchester in connection with Monday's bombing at an Ariana Grande concert.

The Guardian reported that two of those arrested were a man from Libya and his son, while a third person was detained at a separate raid near the home of the family of the suspected bomber.

Twenty-two people were killed and dozens were wounded when a bomb went off at the end of a concert in the English city on Monday night. Great Britain has since upgraded its terror threat, with officials warning another attack could be imminent.

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British security forces deployed 1,000 soldiers Wednesday to protect key sites in London and other locations in the U.K.

The Palace of Westminster, home to the U.K. Parliament, was closed Wednesday, while the Chelsea soccer team canceled its victory parade in London celebrating its Premier League title in the wake of the attack.

U.K. Home Secretary Amber Rudd has identified the bomber as British-born Libyan Salman Abedi, who died in the explosion.

Wednesday's arrests come a day after police arrested another man connected to the attack and searched homes in Manchester.

The Islamic State in Iraq and Syria has claimed responsibility for the attack.