Panama's last two presidents, Ricardo Martinelli and Juan Carlos Varela, faced questions from prosecutors Thursday, each on charges of corruption and money laundering.

Prosecutors have charged Martinelli with corruption over the so-called "New Business" case in which a publishing group was allegedly purchased with public money during his 2009-14 term.

Martinelli, 68, was in a combative mood when he arrived at the public prosecutor's office in Panama City.

"They are violating the law, they are violating the Constitution and international treaties. I hope they will do me justice," the former president told journalists.

"They are fabricating these cases against me. It really is a political persecution."

Martinelli was held in pre-trial detention for two years after he was extradited from the United States to face trial for spying on his political foes. He was acquitted on those charges in 2019.

Varela, 56, meanwhile arrived at the special anti-corruption prosecutor's office to be questioned about alleged illegal donations to his political campaigns from Brazilian construction giant Odebrecht.

"I have come to comply with the subpoena from the public prosecutor's office and to answer any questions they may have," said Varela, who left office last year.

Varela was previously questioned on Monday.

The appearance of the two former presidents "could mean, if there is any optimism, that... no one is above the law," Carlos Barsallo, head of the Panamanian office of Transparency International, told AFP.

But "being realistic and prudent and based on previous experiences, we have to wait and see real and definitive results because in Panama, the perception of impunity has prevailed," he said.

Martinelli won the 2009 election with Varela as his running mate, but their alliance broke down in 2011 when Varela was sacked as foreign minister. Since then, the two former political allies have become enemies.