Greek police said they arrested Saturday a suspect wanted over a series of letter bomb attacks targeting the country's creditors, one of which injured former prime minister Lucas Papademos earlier this year.
"The search continues" for other suspects after an anti-terror police unit arrested a 29-year-old Greek man in Athens, police said in a statement.
The man was known to police for his militant activities, a police source said.
Papademos, who as prime minister from 2011 to 2012 accepted austerity measures to secure a bailout at the height of Greece's financial crisis, was injured when an explosive device detonated as he opened his mail on May 25.
The attack, which remains unclaimed, had a similar methodology to that used by Conspiracy of Fire Nuclei, a far-left group which in March mailed an explosive device that injured a secretary at the International Monetary Fund (IMF) in Paris.
The group had earlier claimed responsibility for a letter bomb, also sent from Greece, discovered at the Berlin offices of German Finance Minister Wolfgang Schaeuble.
The bombs contained gunpowder typically used in firecrackers, police said.
Eight other letter bombs, including those addressed to European Economic Affairs Commissioner Pierre Moscovici and then Eurogroup chief Jeroen Dijsselbloem, were intercepted in the aftermath of the Athens attack.
In 2011, a dozen members of Conspiracy of Fire Nuclei, many of whom were very young, were convicted of "participating in a criminal organisation" and are serving long prison sentences.
After years of crisis and austerity cuts, the Greek economy is still struggling, and experts have said that the country's continued crisis favours youth radicalisation.
In 2012, Papademos's government came under criticism after it negotiated a huge write-down of the country's privately held debt, which led to Greek social insurance funds losing millions of euros in the process. He also served as Bank of Greece governor from 1994 to 2002.