ISTANBUL, (AFP) — Turkish investigators grilled dozens of senior military figures Tuesday, including retired heads of service, over an alleged coup plot as the opposition accused the government of score-settling.

In the most dramatic move to date against the armed forces, anti-terror police detained the suspects Monday over a purported plan codenamed “Operation Sledgehammer” to topple the Islamist-rooted Justice and Development Party (AKP) administration, dating back to 2003.

The suspects allegedly planned to bomb mosques and escalate tensions with Greece in a bid to force the downing of a Turkish jet, thus discrediting the government and ultimately leading to its downfall.

Seventeen retired generals and four active-duty admirals were among those detained and brought for questioning in Istanbul, reports said.

Among them are the ex-air force chief Ibrahim Firtina, former navy chief Ozden Ornek and the former head of the Istanbul-based First Army, Cetin Dogan, who is accused of spearheading the plot.

Although officials have been keeping largely tight-lipped about the detentions, Turkish Prime Minister Recep Tayyip Erdogan confirmed the arrests on Monday during a visit to Spain. Related article: Man held for throwing shoe at Turkish PM.

“Sledgehammer” was first reported in January by the Taraf newspaper, which routinely targets the army.

It said the plan was discussed at a military seminar in March 2003 and published the transcripts of audio tapes that appeared to confirm that some kind of anti-government action was considered at the gathering.

The general staff has said the seminar involved the discussion of war-time contingency plans and denied any coup plot.

Dogan has confirmed the threat of Islamist movements was discussed, but said documents were doctored to include plans to bomb mosques and for the downing of a Turkish plane.

Turkey’s staunchly secularist army has traditionally wielded heavy political influence and unseated four governments since 1960, the last time in 1997 when it forced Islamist Prime Minister Necmettin Erbakan to resign.

The AKP was formed by moderates from Erbakan’s now-banned party.

Turkey’s two largest opposition parties, both the victim of past coups, slammed the government Tuesday over the latest arrests.

Main opposition leader Deniz Baykal questioned why such a massive operation was mounted against retired generals “watching TV at home in pajamas and slippers” over allegations dating back seven years.

“This is obviously a process of political score-settling,” he said.

Nationalist opposition leader Devlet Bahceli said the government was acting with “hatred” and “feelings of revenge” and called for early elections.

Retired and active-duty soldiers are already among dozens of defendants in a controversial case against a network which allegedly planned assassinations and other violence to spark political chaos and prompt a military coup.

Opponents say the AKP has secret ambitions to overthrow the secular system.

The probe into the so-called Ergenekon network, under way since 2007, was initially hailed as a success in a country where all political groups agree military interventions in politics must stop.

But its credibility waned with the arrest of academics, journalists and writers known as AKP critics. Prosecutors relied heavily on anonymous letters and secret witnesses while suspects accused police of fabricating evidence.

Critics say the probe has become an instrument to bully the opposition and discredit the military, seen as the strongest bulwark of the secular system.

The chief of staff has decried a “psychological campaign” to smear the army, asserting that military coups are now a thing of the past.

Monday’s operation followed a row last week between the government and the judicial elite, sparked again by the Ergenekon probe.

The country’s chief prosecutor said he was examining whether the government exerts pressure on the judiciary, a move that may in theory result in a bid to seek AKP’s closure at the constitutional court.

In 2008, the AKP narrowly escaped being banned for violating Turkey’s secular system.