Hackers made a "very powerful" attack on the Kremlin website on Sunday, the Russian government said on Monday.

Kremlin spokesman Dmitry Peskov linked the attack to regional elections in Russia on Sunday in which the opposition sought to challenge government-allied politicians in the one region it was allowed to run.

Peskov said the election commission's website came under attack on Sunday morning.

"Given that, you will certainly be interested to know that from 5 to 10 am on Sunday a very powerful attack was simultaneously carried out on the Russian president's website," Peskov told reporters.

"Defense systems worked though it was not easy, the attack was rather strong," he said.

He said had no information on who might have been behind the attack.

Russia has a hacking criminal underground and the United States regularly accuses Russian, as well as Chinese, hackers of attacks.

Experts say Russian government-backed hackers target U.S. government computers as well as help spread Moscow propaganda at a time of dire relations between Kremlin and the West over the conflicts in Ukraine and Syria, human rights and other issues.