ISTANBUL — Turkish police launched an operation on Tuesday to arrest 70 soldiers accused of links to the US-based preacher alleged to have orchestrated last year's attempted coup, the private Dogan news agency reported.

Operations targeting supporters of cleric Fethullah Gulen are continuing on a daily basis some 15 months after the failed putsch. Gulen has denied involvement. In the last week alone, around 800 people were held over alleged ties to him.

Among those targeted in the police raids, focused in the central Turkish city of Konya but launched simultaneously across seven provinces, were two colonels, seven captains and 36 lieutenants, Dogan said.

Sixty-two of the suspects were in the air force, some of them pilots, it added. Police were conducting searches of their homes and places of work.

More than 50,000 people have been jailed pending trial over links to Gulen, while 150,000 people have been sacked or suspended from jobs in the public and private sectors since the July 15 coup attempt, in which 250 people were killed.

Some of Turkey's Western allies and rights groups have voiced concern that the government is using the coup investigations as a pretext to crack down on dissent.

Ankara argues that only such a purge could neutralize the threat represented by Gulen's network, which it says infiltrated institutions such as the military, judiciary and schools.

A sharp escalation in tensions between Turkey and NATO ally the United States this week was triggered by the arrest of a Turkish employee of the US consulate in Istanbul whom Ankara accuses of links to Gulen.

Almost 150 former Turkish military personnel went on trial Monday over clashes on an Istanbul bridge during last year's failed coup that claimed dozens of lives, including a key aide of President Recep Tayyip Erdogan.

The bridge across the Bosphorus strait in Istanbul was the scene of bloody fighting between Erdogan's supporters and renegade soldiers seeking to oust the elected government on the night of July 15, 2016.

It was later renamed by the government as July 15 Martyrs' Bridge.

The dead included Erdogan's campaign manager Erol Olcok and his 16-year-old son Abdullah Tayyip, who were killed when soldiers opened fire on protesters on the bridge which connects Asia and Europe.

Erol Olcok had named his son after Erdogan and his predecessor as president, Abdullah Gul.

A total of 143 suspects, including 30 officers, appeared in court. All the suspects barring eight are being held under arrest.

They are accused of crimes ranging from murder to attempting to overthrow the parliament and the government, according to the 1,052-page indictment.

If convicted, the suspects each face 37 life sentences, according to the state-run Anadolu news agency.

Many civilians rushed to the bridge on the night of the coup, heeding Erdogan's call to quash the putsch bid, but the renegade soldiers then shot at them.

Fatmanur Goksu, 24, was one of those shot on the bridge as well as her father.

"The same bullet hit my arm and then my father's," she told AFP outside the court, where some of the victims' relatives gathered wearing T-shirts with the word "martyr" and the name of their dead loved one.

Goksu said she got out onto the streets "without any second thought" after Erdogan's call.

Thirty-four civilians and seven coup plotters were killed on the Bosphorus bridge, according to the indictment.

But by the early morning hours, the soldiers surrendered to police, laying down their arms on the bridge and raising their hands in an enduring image of the coup's defeat.

Erdogan attended the funeral of the Olcoks and others two days after the coup bid, weeping openly in a rare show of emotion.

"We're here today to settle accounts with those who attempted to invade our country," Mahir Unal, ruling Justice and Development Party (AKP) spokesman told reporters before the trial began.

Monday's trial is one of several legal processes seeking to bring to justice those believed to have played a role in the coup bid which left 249 people dead, not including the putschists.

Veysel Kilic, the father of one of the military academy students being held, said he did not have any hope in the "unsound" justice system.

Kilic took part in the main opposition leader Kemal Kilicdarogu's month-long foot march in July to protest against alleged injustices under Erdogan.

Like many relatives, Kilic said his air force academy student son was "deceived" and "told to join an unplanned exercise to measure their obedience to their commander".

"The students were totally unaware. They did not fire. Those children remained neutral," adding that more would have been killed if the students had taken sides.

Last week, a court in southwestern Turkey handed life sentences to 40 people convicted of plotting to assassinate Erdogan at an Aegean hotel.

Erdogan has vowed to purge all state institutions to clean the "virus" of US-based Muslim preacher Fethullah Gulen whom his government blames for the putsch.

The cleric, who lives in Pennsylvania, has denied any involvement. — Agencies