3 foreigners are among the 13 people detained by Turkish police over Istanbul airport attack

Turkish police have detained 13 people, including three foreigners, in connection with the triple suicide bombing at Istanbul's main airport which killed 42 people, a Turkish official said on Thursday.

Police conducted simultaneous raids on 16 places in Istanbul, the official told Reuters.

The attack, which Turkish officials blamed on ISIS early on, has not yet been claimed by any terrorist group.

Turkey declared a day of national mourning after the deadliest and most high-profile attack in a string of killings and bombings that have gripped the country this year.

Foreign heads of state have expressed their solidarity with Turkey and presented their condolences, but for the Turkish Foreign Minister Mevlut Cavusoglu, it is "not enough" to show solidarity in response to terrorist attacks.

Cavusoglu made the comments at a news conference in Brussels to announce the "opening" of Chapter 33 in Turkey's European Union accession process, which covers budget policy.

Cavusoglu also said that he expects European Union to meet its commitments regarding the visa liberalisation.