The TV footage showed Protasevich -- who could face 15 years in jail -- with dark markings on his forehead, saying he was being treated "according to the law."
In a statement after the meeting, Mitsotakis said the two leaders "agreed on the immediate resumption of talks between Greece and Libya on the delimitation of the maritime zones".
In response, the Football Federation of Kosovo (FFK), said in a statement that "Kosovo is an independent state" and threatened not to play the match if it was not allowed to use its national anthem and flag.
Among the foreign dignitaries attending are Russian Prime Minister Mikhail Mishustin and Britain's Prince Charles, with France represented by Defence Minister Florence Parly after President Emmanuel Macron pulled out over the pandemic.