A Turkish court's landmark conviction of some 300 military officers accused of plotting to oust an elected government sends a stark warning to the armed forces, whose dominance may have reached its end, according to analysts.

The civilian court sentenced at least 325 officers to prison terms ranging from 12 to 20 years, at the end of a two-year trial that finally ruled that an army exercise in 2003, named "Sledgehammer," was an undercover coup plot.

The verdict brought a divided emotional reaction across the political spectrum in Turkey, which has seen four coups in half a century with none of their perpetrators yet convicted.

"Even the mightiest of commanders are now being held accountable in courts. That is a positive development," Deniz Zeyrek, Ankara bureau chief of the daily Radikal, told AFP.

But Zeyrek noted that the process was not perceived as "meticulous enough" by the public, saying the reasons for the court decision should be clearly explained in the justified ruling, which currently remains pending.

Turkey needs to hear the grounds for the conviction of its generals before a judgement on the outcome can be made, a political analyst agreed.

"The ruling is a historic turning point, if there really has been a crime which met its punishment," professor Mensur Akgun from Kultur University said.

"If the legal process failed to operate, then the outcome is disturbing."

The three "masterminds," former First Army commander Cetin Dogan, former air forces commander Ibrahim Firtina and former naval chief Ozden Ornek initially received aggravated life sentences -- the heaviest possible since Turkey abolished the death penalty in 2004.

But their sentences were immediately commuted to 20 years, on the grounds that their plan to unseat the Islamic-rooted government fell through "due to reasons beyond their control," the court stated.

Only 36 defendants were acquitted among the 365 suspects, all of them retired or active military officers. The rest were handed at least 12 years in prison for their role in trying to "incapacitate the parliament from functioning by force."

"The Sledgehammer landed heavily," read Radikal's headline on Saturday, while the pro-opposition daily Cumhuriyet criticised the ruling with: "Sledgehammer, strike to justice."

The so-called Sledgehammer plans were first brought to light in January 2010, after leaked army information was publicised by the liberal Taraf daily, which hailed the verdict with the headline: "It is now much more difficult to attempt coups."

The evidence included documents, diary entries and sound recordings of some of the generals, outlining plans to bomb mosques to provoke internal conflict, as well as to stir chaos with neighbouring countries, which would have paved the way for a military takeover to restore peace.

The charges triggered a vehement reaction, with defendants openly suggesting that the trial was being used by the ruling Justice and Development Party (AKP) to strike down the all-powerful army, the self-appointed guardian of secularism.

"I find the verdict too heavy. The accusations are grave, so the ruling needs to be convincing," Hikmet Sami Turk, former justice and defence minister said.

"I believe such decisions have negative affects on army morale, at such a critical time when there is the Syrian crisis on the doorstep and the Kurdish problem inside the borders."

Critics have repeatedly claimed the trials are part of a witch-hunt by the government to silence opposition in order to increase its grip.

The government, which came to power a year before coup plans were allegedly drafted, gave a cautious initial reaction.

"We need to follow and see the decision of the supreme court of appeals. We all expect a rightful decision to come out from there," Prime Minister Recep Tayyip Erdogan told reporters in Ankara.

As some raised questions on the shortcomings of the trial, others praised the verdict as a legal victory that could finally put the lid on the military tradition of interfering in politics.

"This decision will put an end to the military tutelage," Nazli Ilicak, columnist for government-friendly Sabah daily told NTV.

But she added, "It is going to be deterring for both civilian and military spheres."