Turkey's highest appeals court has overturned the convictions of 275 people, including senior military officers, accused of plotting a coup, BBC News reports.

The appeals court ruled that the convictions were unsafe because the existence of a clandestine network called Ergenekon was unproven.

The officers, journalists, lawyers and academics were found guilty in 2013 of plotting the overthrow of then-prime minister Recep Tayyip Erdogan.

The new ruling may lead to a retrial.

The Ergenekon trial was one of the biggest court cases in recent Turkish history, pitting Erdogan's supporters in the Islamist-rooted AK Party against the secularist military establishment.

The highest-ranking defendant was ex-military chief Ilker Basbug, who had been given a life sentence. Several other life sentences were also handed down.

The appeals court found several other flaws in the original proceedings, including illegal surveillance and searches.

The Ergenekon network was accused of plotting a coup against Erdogan - now Turkey's president - in 2003-2004.