Security is being stepped up in major European cities ahead of New Year celebrations, with officials wary of possible terror plots.

It is technically feasible to maintain archaeological finds unearthed during the prolonged excavations for a new metro in the northern city of Thessaloniki and at the same time to complete the necessary underground tunnels, Infrastructure and Transport Minister Christos Spirtzis said on Tuesday.

"The brutal criminals of Daesh are enemies of the Democracy and the Civilization and commit crimes against Humanity. And as such they must be treated immediately and efficiently," President Pavlopoulos said on Wednesday while receiving 21-year old Nadia Murad Basee Taha who managed to escape from ISIS.