ATHENS, Greece (AP) — Dimitrios Ioannidis, the feared security chief who led a countercoup against Greece's military leaders and provoked Turkey's invasion of Cyprus in 1974, has died. He was 87.

Ioannidis, who was jailed for life for his part in the 1967-74 dictatorship, died Monday in an Athens hospital, a day after experiencing breathing problems in his prison cell, the justice ministry said.

He had spent the past 35 years out of the public eye in a special wing of the maximum security Korydallos prison, which was built during the military regime.

As head of the brutal ESA military police, Brigadier Ioannidis was a key figure in the military dictatorship that seized power on April 21, 1967 after years of political instability.

The ultraconservative dictators imposed martial law and cracked down heavily on political opponents, imprisoning or exiling thousands, many of whom were tortured by ESA.

The junta was condemned in the West, and the U.S. temporarily banned arms sales to Greece. But a 1971 visit by Vice President Spiro Agnew, who was of Greek descent, was viewed by many as tacit approval of the dictatorship.

This led to a surge in anti-American sentiment in Greece, and in 1999 then U.S. president Bill Clinton conceded that Washington had failed its "obligation to support democracy."

Following a student pro-democracy uprising that the army crushed in November 1973, dictator George Papadopoulos tried to slowly introduce some democratic reforms.

But army hard-liners, led by Ioannidis, staged a successful countercoup on Nov. 25 1973 and ruled Greece with increasing harshness and incompetence for the next eight months.

Although Ioannidis appointed a military president and a civilian prime minister, he was the real man in control, and became known as the "invisible dictator." Under his regime, relations with neighboring Turkey — as well as President Makarios' government in Cyprus — quickly deteriorated.

In mid July 1974, the military overthrew Makarios, prompting Turkey to exercise its rights as a guarantor power on the Mediterranean island and invade on July 20. The attack caught Athens unprepared, and the dictatorship ended with a return to civilian government after four shambolic days in which Greece came close to war with Turkey.

A second Turkish advance in August gave Ankara control of nearly 40 percent of the island, whose continued partition along ethnic lines remains a major thorn in gradually thawing relations between NATO allies Greece and Turkey.

The coup leaders were tried in 1975 and jailed in Korydallos. Papadopoulos died in 1999, aged 80. The only surviving senior junta figure is Brig. Stylianos Pattakos, who has been freed from jail.

In 2008, authorities rejected an application by Ioannidis for temporary release from prison on health grounds.

No funeral arrangements for Ioannidis have been announced.