Tusk's 'Kremlin' tweet prompts Polish uproar

"Alarm! A vehement dispute with Ukraine, isolation in the European Union, departure from the rule of law and independent courts, attack on non-governmental sector and free media - PiS strategy or Kremlin's plan? Too alike to rest easy," he said.

Beata Szydlo, the ruling Law and Justice (PiS) party PM, reacted at 5.45AM, saying that Tusk "has done nothing for Poland" as EU Council chief and that in "using his position to attack the Polish government, he is attacking Poland".

The exchange prompted tens of thousands of retweets and comments on social media.

Lech Walesa, the Polish Nobel laureate, applauded Tusk's words, saying they were "the last bell, to save Poland for a democratic Europe".

A PiS senator, Stanislaw Karczewski, said Tusk was "banging his head against a wall" in what would "hurt him".

The Polish foreign minister, Witold Waszczykowski, told Polish press later the same morning that Tusk's comment was "some kind of mournful cry of frustration".

"He can't actively stay in European politics, so he's trying to come back to Polish politics," the minister said.

Tusk had referred to a current Polish dispute with Ukraine over the exhumation of Polish people slaughtered there by Ukrainian soldiers in World War II.

He also referred to Poland's "isolation" over PiS judicial reforms deemed by the European Commission to violate judges' independence and deemed worthy of EU sanctions by the European Parliament.

The parliament's resolution, passed last week, included an outcry over a recent march by ultra-nationalist groups in Warsaw.

Tusk's intervention comes ahead of Polish elections in 2019.

If Tusk returned to Poland to fight for office after he stepped down from his EU Council post the same year, he could end up squaring off against the PiS party leader, and his old nemesis, Jaroslaw Kaczynski.

Waszczykowski, the foreign minister, spoke at length on Tusk.

He said Tusk had been ineffective on Brexit, on the Catalonia crisis, and on Ukraine.

He also said Tusk was so subservient to Commission chief Jean-Claude Juncker that Juncker had proposed to merge the two posts in future.

"It's him [Tusk] who's isolated. The effect is Juncker's latest proposal, to liquidate that [Tusk's] post, joining it to the post of European Commission chief," Waszczykowski said.

Old enmity

The Tusk-Kaczynski enmity was sealed in the Smolensk air disaster in 2010, in which Jaroslaw Kaczynski's brother, Lech Kaczynski, the then Polish president, and 95 others died.

Jaroslaw Kaczynksi has accused Tusk of conspiring with Russia on the incident, with Tusk grilled for eight hours in April in a Polish intelligence probe.

Judicial reforms aside, PiS is also in violation of EU decisions on sharing asylum seekers and on logging in a nature reserve.

It faced more concrete Kremlin allegations earlier this year.

A book by a Polish investigative journalist said in July that Poland's hawkish defence minister, Antoni Macierewicz, had ties to Russian intelligence.

A report by German newspaper Frankfurter Allgemeine Zeitung said at the same time that Macierewicz's deputy, Bartosz Kownacki, also had ties to pro-Kremlin far-right groups suspected of espionage.