Turkey's government has suggested it may retaliate against the perpetrators of a deadly bomb attack in Istanbul.

The country's security authorities are blaming militant groups, including the Kurdistan Workers' Party, or PKK, for the attack.

A bomb exploded Sunday on a busy shopping street in Turkey's largest city, killing at least six people and injuring 81 others.

The authorities say they have detained a Syrian woman suspected of having planted the bomb, as well as about 50 others.

The Syrian woman reportedly told investigators she was trained by the PKK and other Kurdish militant groups, and had entered Turkey through northwestern Syria. The PKK is listed as a terrorist organization by Turkey.

Interior Minister Suleyman Soylu told reporters on Monday the Turkish government knows what message the perpetrators wanted to send to it. He said the government will pay them back heavily in return.

Many citizens visited the site on Monday and laid flowers for the victims.