A spokesperson for Turkey’s President said the country will increase security following a spate of cyber attacks last week that affected government websites and some banks.

Ibrahim Kalin, a spokesperson for President Recep Tayyip Erdogan, told reporters earlier this week that authorities were investigating the source of the cyber attacks that disrupted access to government websites and online bank transactions.

Kalin said the cyber attacks were “successfully repelled” and the attempt to cause chaos had failed.

The hacking collective known as Anonymous had threatened to attack in retaliation for the country’s alleged support for the Islamic State group through the purchase of its oil - a claim Turkey vehemently denies.

Others have suggested that the attacks may originate from Russia in response to Turkey’s downing of a Russian plane last month.

A non-governmental organization that administers addresses for websites using the “tr” domain, said Thursday that the attack appeared to be from “organized sources” outside Turkey.

The domain is used by websites belonging to Turkish ministries, commercial enterprises and banks.

Transport and Communications Minister Binali Yildirim called it a “serious” attack and asked an Ankara-based University to beef up security measures, saying they were “insufficient.”

Banking sources said the attack has seriously disrupted transactions.

Experts have been unable to identify the source of the attack.