Egyptian security officials say a gunman has killed two Coptic Christian brothers in an attack on a liquor store in Giza province, just days after nine people were killed in an attack on a church and store in Cairo.

The officials said Monday the attack took place on New Year's eve, a busy night for liquor stores.

They say it is unclear whether the attacker was an extremist.

The officials requested anonymity because they were not authorized to brief the media.

Friday's attack in Helwan suburb left eight Copts and a policeman dead. It was claimed by the Islamic State group.

Egypt's Christian minority has been targeted by Islamic militants in a series of attacks since December 2016 that left more than 100 dead and scores wounded.