Donald Tusk questioned by Polish investigators over 2010 plane crash
Polish investigators have questioned Donald Tusk, president of the European Council, as a witness in an investigation into the 2010 plane crash that killed President Lech Kaczynski.
The case is widely seen as a politically-driven attempt to discredit the EU leader.
Mr Tusk was the Polish prime minister at the time of the crash, which occurred in Russia and killed 96 people, many of them top Polish state and military officials.
Prosecutors said they are trying to determine why Polish authorities of the time did not take part in the post-mortem examinations, which were performed by Russians and later shown to be sloppy.
Exhumations have revealed that body parts got mixed up and were buried in the wrong graves.
But Mr Tusk's Polish supporters see the questioning as part of a political feud going back years that pits him against Jaroslaw Kaczynski, the late president's twin brother and the head of the ruling Law and Justice party in Poland.
Mr Kaczynski holds no government position but is widely seen as the man who directs all major government decisions.
Ahead of Thursday's questioning in Warsaw, Mr Kaczynski warned that Mr Tusk "should be afraid".
Katarzyna Lubnauer, a politician with the opposition Modern party, said calling Mr Tusk to give evidence was an act of "political revenge and an attempt to humiliate the former prime minister".
Mr Tusk's lawyer Roman Giertych also said he believed "political motivations" were behind the decision to question him.
Mr Tusk was also questioned as a witness in a separate investigation in April.
He is considered one of the most charismatic and effective politicians that Poland has had in many years, and the only one able to unite a weak and divided political opposition.
Should he ever return to Polish politics, he would represent a major threat to Mr Kaczynski, who is pushing an agenda for radical change considered an attack on democratic norms by the EU and many other international observers.
Mr Tusk - who has openly criticised the Polish government - is often mentioned as a possible candidate in presidential elections in 2020, soon after his tenure as European Council leader is scheduled to end.
Dozens of supporters greeted him as he arrived at the prosecutor's office on Thursday morning.
Mr Kaczynski, a former prime minister who lost to Mr Tusk's Civic Platform party in 2007, has long accused Mr Tusk and Russia of responsibility for the tragedy that killed his brother.
Mr Tusk vehemently denies that, and in turn accuses Mr Kaczynski of cynically using the tragedy for political purposes.
Last month Mr Kaczynski lashed out at opposition politicians trying to block the disputed judicial overhaul.
When an opposition politician said the late president Lech Kaczynski had blocked Jaroslaw's past attempts to take drastic steps against the judicial system, Mr Kaczynski shouted from the podium in parliament: "Don't wipe your treacherous mugs with the name of my late brother. You destroyed him, you murdered him, you are scoundrels."