Hundreds of protesters burnt flags outside the Hungarian consulate in the Armenian capital, Yerevan. The extradition of a prisoner to Azerbaijan has fueled tension in the Caucasus.
The AFP news agency reported that several hundred angry demonstrators burned a flag and threw eggs and tomatoes outside the Hungarian consulate on Saturday.
They were upset with Hungarian authorities for sending a prisoner who had murdered an Armenian national back to his native Azerbaijan, where he was pardoned.
Azerbaijani Lieutenant Ramil Safarov had been serving a prison sentence in Hungary, where he had killed an Armenian officer while both were attending a training course at a military academy in the capital, Budapest, in 2004.
The Azeri soldier confessed that he had hacked the victim to death in revenge for his comments allegedly insulting Azerbaijan. The murderer was then sentenced to life in prison by a Hungarian court and extradited now, after having served eight years of his sentence.
Instead of having him serve out his sentence, Azerbaijan pardoned the murderer upon his return, reinstated him to the army and promoted him to the rank of major.
This prompted Armenia to cut diplomatic ties with Hungary, accusing it of having struck a deal to secure energy deliveries from oil-rich Azerbaijan, with which it has been developing close economic ties.
The latest flare-up highlights tensions in the volatile Caucasus region. Relations between neighboring Armenia and Azerbaijan, two former Soviet republics, are tense.
They fought a war over the disputed region of Nagorny Karabakh in the 1990s, when Armenian-backed separatists had seized the region from Azerbaijan. The fighting left some 30,000 people dead.
Despite a cease-fire in 1994, there has not been a final peace deal, and firefights still erupt frequently along the Karabakh frontline despite international mediation efforts by Russia, France and the United States under the auspices of the OSCE.
US President Barack Obama has reacted to the latest developments and said he was "deeply concerned" about Azerbaijan's actions.
This criticism was rejected by Azerbaijan, which has insisted the pardon of the soldier was in line with a European legal convention on extradition.
rg/mkg (AFP, dpa)