"A denial of service attack is taking place against the parliament's external website," parliament said in a statement.

The attack began around 2:30 pm (1130 GMT), slowing down or completely denying access to the site.

Several hours later there was still no official confirmation of who was behind the incident.

"The parliament is taking steps to limit the attack," the statement said.

Finnish news agency STT was targeted in a cyber attack at the end of July, restricting its news and image distribution for several days.

In April, Finnish defence ministry and government websites were also subjected to similar cyber attacks but their problems were quickly resolved.

The Finnish Security and Intelligence Service (SUPO) warned in May that "Russia has the will" to influence Finland's NATO application process and that "various attempts to do so are to be expected".

SUPO director Antti Pelttari estimated the country would face "an increasing number" of cyber attacks.

Denial of service attacks "try to give the impression that society is paralysed, but they are not capable of causing actual destruction", Pelttari said in April.