Angry Ukrainian internet users are being blamed for deluging the social networking sites of German Chancellor Angela Merkel with abuse over her "cosy relationship" with Russia.
Tens of thousands of malicious images and insults have been put on Mrs Merkel's Facebook page.
Her office said it was a slanderous, racist and extremist "spam attack".
The official Facebook page of French President Francois Hollande has also been targeted.
Germany and France have been at the forefront of efforts to rejuvenate a stalled peace deal in Ukraine that would lead peace talks between it and Russia.
The BBC's Stephen Evans in Berlin says that the doctored pictures liken the chancellor to Nazi leaders including Hitler and his Foreign Minister Joachim von Ribbentrop.
Our correspondent says that while the origin of tens of thousands of derogatory comments is unclear, they invariably relate to Ukraine and Mrs Merkel's alleged closeness to President Putin of Russia.
She was filmed sitting near him at the World Cup Final in Brazil, but the common perception within Germany is that she is actually deeply opposed to any Russian attempts to annex or destabilise parts of Ukraine, he adds.
The speculation in Germany is that the abusive images have either been put there by enraged Ukrainians who are fiercely against Russia, or by some Russian source which wants to drive a wedge between the Ukrainian government and Germany, our correspondent says.
The comments provoked a terse reply from Mrs Merkel's media team.
"Dear fans of the Angela Merkel site, there is currently a spam attack on this page that floods all posts with certain comments," a message on it read.
It said that the malicious comments would be deleted.
Mr Hollande's official Facebook page was hit by harsh criticism of the move by France to sell Mistral warships to Russia despite allegations in the West that Russia is fomenting the conflict in Ukraine.
Correspondents say that both Russia and Ukraine are often accused of inundating media outlets with comments - sometimes hostile - about or relating to the conflict.