Viktor Orbán has generated fresh controversy by posting a historical map of 'Greater Hungary' on Facebook.
Hungary's prime minister posted his support for students taking their examinations on Wednesday, accompanying the message with an image of Hungary's former territory before the end of the First World War.
This historical territory included large parts of modern Croatia, Serbia, Romania and Slovakia – which were all lost under the Treaty of Trianon of 1920 following the collapse of the joint Austro-Hungarian state.
Hungary lost around two-thirds of its territory and some citizens in the country consider the treat a national tragedy. Similar maps have also been displayed at far-right rallies.
Leaders of two neighbouring countries have responded to this gesture on Facebook.
On Thursday, Croatian President Zoran Milanovic urged students not to publish any old maps on social media.
"In our cabinets and archives there are numerous historical cards and maps that show our homeland much bigger than it is today," Milanovic wrote on Facebook, adding that other European countries will also have similar claims.
"Don't 'share' them and put them on your profile - they are not relevant or effective today, and more importantly, they are endlessly annoying our neighbours."
"Croatia is a modern European country and nation ... learn from history, but look into the future."
Croatia's foreign minister, Gordan Grlić Radman, has also added that relations between Hungary and Croatia are excellent, but that territorial claims were unthinkable in the EU.
This is not the first time that Orbán has shared images the map of "historic” Hungary, and the Croatian prime minister said in December that his government would “hold talks with the Hungarian side” about such matters.
Additionally, Romania’s Prime Minister Ludovic Orban reacted sarcastically to his Hungarian counterpart late on Wednesday by using a Romanian proverb.
Hundreds of Romanian users have also responded to Viktor Orbán on Facebook.
Romania remains home to a large ethnic Hungarian community, but on Wednesday, the country's parliament rejected an initiative to declare the Hungarian language official in Transylvania.
The decision had generated an angry response from the Democratic Union of the Hungarians in Romania (UDMR), who are closely related to Viktor Orbán's Fidesz party.
"We are asking for what the constitution provides," said the UDMR on Facebook.