Georgian police on Saturday questioned a former prime minister over the alleged use of a fake passport, further raising tensions between the government and President Mikheil Saakashvili, who says his allies are being persecuted.

"An investigation was opened into the use of a forged document and an attempt of illicit crossing of the state border," an interior ministry statement said.

Saakashvili's closest ally and the general secretary of his United National Movement party, Vano Merabishvili has rejected the accusation and denounced it as politically motivated.

Saakashvili's allies have alleged persecution after the arrests of his former defence minister, the army's top general and several interior ministry officials since the new government led by Prime Minister Bidzina Ivanishvili was brought to power by polls last month.

"I want to tell Bidzina Ivanishvili that he can't scare us with intimidation, blackmail and arrests," Merabishvili told journalists before interrogation.

Once one of Georgia's most powerful politicians, Merabishvili oversaw popular and internationally-praised reforms which eradicated bribe-taking in the ex-Soviet country's police force.

Released after three hours of questionning, he made an emotional statement saying his "presence here at the police is very symbolic."

"It is regrettable that today the police and the interior ministry are being used by Ivanishvili as a repressive machine against disstent," he said, his voice trembling.

The interior ministry said Merabishvili used a passport bearing his picture but issued under an alias at Tbilisi airport while accompanying Saakashvili on Friday's official visit to neighbouring Armenia, where they met European Commission President Jose Manuel Barroso.

In a statement on his Facebook page, Saakashvili has said the accusation was an "absurd conceived by reckless people" and called on police to drop charges against Merabishvili.

"I express concern over the instances of political persecution," the statement reads.

The arrests of former government members have raised an international outcry, with top diplomats warning Georgia against what EU foreign policy chief Catherine Ashton said could be perceived as "selective justice" and "retribution against political rivals."

Ivanishvili has denied that the cases are politically motivated but has said that alleged crimes committed under the nine-year rule of Saakashvili's former government must be dealt with.

The arrests have also complicated the political cohabitation between Ivanishvili and Saakashvili, who despite his party's electoral defeat, retains the presidency for another year.

[Image via Agence France-Presse]