Tense crowd awaits Tusk in Poland as he is to testify

Tusk, a former prime minister, will appear before prosecutors in Warsaw to answer questions in an investigation into suspected collaboration between Russian and Polish intelligence services.

The website of SKW said that the investigation was initiated regarding in a case concerning the cooperation of SKW with the Federal Security Service of Russia (FSB).

Jaroslaw Kaczynski, the powerful head of Poland's governing rightwing Law and Justice (PiS) party, has accused political arch-rival Tusk of "moral responsibility" for the death of his brother Lech in the air crash in Russian Federation.

I have no doubt that this is part of a political smear campaign. Tusk is to be questioned by prosecutors in Warsaw as a witness.

Using his personal Twitter account, Mr Tusk said: "It was Hitchcock, who directed Brexit: first an natural disaster and the tension rises". "I have come here because of respect for the Polish state", he said.

The European Council president is expected to arrive at Warsaw's central railway station at 0840 GMT from his home city of Gdansk.

In their chants, Tusk's supporters said he beat Kaczynski 27-1.

Speaking to reporters after the questioning, the former liberal Polish prime minister said: "This whole affair is extremely politically motivated".

Kaczynski, 67, holds no government post but is seen as Poland's main decision-maker.

"I would be an exception in Poland if I said that this is a neutral case, that everything here is honest, and not fraught with political emotions", he said, adding that the probe contains elements of "political persecution".

Donald Tusk has been summoned to give evidence to a secretive investigation.

The euroskeptic PiS party, which defeated PO in a 2015 election, has been accused by the EU's executive arm, the European Commission, of undermining rule of law and democracy following the party's overhaul of the constitutional court.

Tusk's lawyer Roman Giertych said earlier this month that prosecutors had threatened twice to use physical force against the former prime minister to bring him to the hearing despite his European Union immunity.

Various members of the PiS party, including leader Jarosław Kaczyński, have suggested that Tusk should face criminal charges in Poland related to a number of ongoing investigations, including the Amber Gold pyramid scheme which collapsed during Tusk's term in office, as well as the preparations related to the presidential plane crash in Smolensk, western Russian Federation, on 10 April 2010.

Kaczynski has accused Tusk of "moral responsibility" for the death of his brother Lech in the plane crash.