A series of coordinated cyber attacks by hackers interrupted services on the websites of the Russian presidential administration and the central bank, officials said Friday, March 14, according to RIA Novosti.

“A powerful attack on the site is ongoing,” a spokesperson for the Kremlin said Friday. “Measures are being taken to restore the normal functioning of the site.”

Bank of Russia said in a statement that its website had been offline for about an hour Friday morning following a denial of service attack. A source at the central bank told Prime business news agency that the origin of the attack remained unknown.

By early Friday afternoon the two websites appeared to be functioning normally, RIA Novosti said.

The attack on Russia’s central bank was not the first such incident. Hackers brought down the bank’s site for seven minutes in October during another coordinated strike.

An official at the central bank later said that attack was believed to be linked to the Islamic anti-Russian group Anonymous Caucasus.