Rotterdam police have issued an amber alert following the disappearance of a 12-year-old girl, saying they are extremely concerned about her safety.

Hania left school on Thursday at around 12 am, telling her teacher she had to visit the orthodontist. But she did not have an appointment and failed to return home in the afternoon.

‘When we began looking into that, we became extremely worried about her welfare,’ a police spokesman told the AD.

Politie en familie maken zich ernstige zorgen over het welzijn van de 12-jarige #Hania. Heeft u ook maar het kleinste beetje informatie over waar zij kan zijn bel dan met de politie via 0800-6070. https://t.co/UXtfNtuENW. pic.twitter.com/eM3RyVRXh7

— Politie Rotterdam eo (@Politie_Rdam) June 28, 2019

Hania was wearing a white flowery skirt, white leggings, a black jacket and carrying a pink rucksack on the day she disappeared.

Family members have reportedly told police about worrying online chats Hania had been having, which have since been wiped.

Police are urging anyone who may have seen the girl to contact them on 0800 6070.

An amber alert is a nationwide warning issued by police when a child disappears under suspicious circumstances.