ISTANBUL (AFP) - A Turkish court on Friday ordered the immediate release of former military chief Ilker Basbug, who was sentenced to life in prison last year for plotting to overthrow the Islamic-rooted government, his lawyer said.

The decision came a day after Turkey's top Constitutional Court ruled that Basbug's legal rights had been violated.

"This verdict is significant," Basbug's lawyer Ilkay Sezer told reporters. "Mr Basbug will walk free three hours later," he added.

Basbug was sentenced to life in prison in 2013 along with hundreds of military officers who were given long jail terms for their role in the so-called "Ergenekon" conspiracy, an alleged plot to overthrow the government.

The military, which sees itself as the guarantor of Turkey's secular principles, has carried out three coups - in 1960, 1971 and 1980, - and pressured an Islamist government to step down in 1997.

Prime Minister Recep Tayyip Erdogan has spent the best part of his 11 years in power trying to curb the military's influence.

But he has recently sought to get the army back on his side as he fights for political survival in a bitter feud with his ally-turned-opponent Fethullah Gulen, whom he accuses of masterminding a graft scandal to topple him.

In a conciliatory gesture toward the army that further increases the chances of retrials for the hundreds of convicted officers, parliament in February abolished the specially appointed courts that tried them.

The Constitutional Court's ruling could set a precedent for more than 200 others jailed for their alleged roles in coup-plotting.