Lithuania has been hit by what appears to be a concerted cyber assault by pro-Russian hackers.
The national communication regulator's office said that some 300 websites, including those of public institutions such as the national ethics body and the securities and exchange commission, as well as a string of companies, had found themselves under attack.
The sites' content was replaced with images of the red flag of the Soviet Union, along with anti-Lithuanian slogans.
Lithuania broke free from the Soviet Union in 1991 after five decades of rule from Moscow, and joined the EU and NATO in 2004.
Its relations with Russia have been on a downturn in recent months, after Vilnius adopted a harder line in a string of long-running bilateral disputes.
Last week, Estonian television ETV24 reported that there had been multiple appeals on Russian Internet forums, calling for Russian hackers to unite and launch a large-scale attack on the websites of Latvian, Lithuanian and Estonian government institutions.
ETV said the hackers planned to replace the original content of the websites that they hack into with huge red stars and photographs of Soviet soldiers.
Ukraine was also to be targeted, it said.
In April, Lithuania unilaterally blocked EU attempts to kick off talks on a new partnership deal with Russia, to replace the old deal signed in 1997 when Moscow was still reeling from the Soviet collapse.
Estonia was hit by massive cyber attacks last year after the authorities decided to move a Red Army memorial from the centre of the capital Tallinn.
And Ukraine and Russia have been at odds for several years over oil transit and pricing arrangements.
