Tens of thousands of supporters of Turkey's ruling and main opposition parties, usually bitter foes, rallied together on Sunday in support of democracy following a failed military coup as President Tayyip Erdogan tightens his grip on the country.

Demonstrators held a cross-party "Republic and Democracy" rally in Istanbul's central Taksim Square in a spirit of unity following the failed coup, in which at least 246 people were killed and more than 2,000 injured.

In a rare move, pro-government channels broadcast a live speech from the podium by main opposition leader Kemal Kilicdaroglu.

"This is a day to unite, a day to stand up against coups and dictatorial regimes, a day to let the voice of the people be heard," he said at the rally, organised by his secularist opposition CHP but also backed by the ruling Islamist-rooted AK Party and by other opposition groups.

"We are all together in Taksim today. Today is a day we made history all together."

Erdogan will probably try to capitalise on the large size of the crowd of all political persuasions to try and reassert full control over the country, a NATO ally and an important partner in the U.S.-led fight against Islamic State.

In another demonstration of unity after the coup, which was staged by a faction within the armed forces, the head of Turkey's air force issued a rare statement stressing "absolute obedience" to the chief of the military General Staff. Some members of the air force were involved in the coup.

The chief of the military General Staff, Hulusi Akar, who was held hostage by the plotters on the night of July 15, condemned the plotters on Sunday as "cowards in uniform" who had greatly harmed the nation and the army.

Erdogan, who narrowly escaped capture and possible death during the attempted coup, has declared a state of emergency, allowing him to sign laws without prior parliamentary approval in a drive to root out supporters of the coup.

His critics fear he is using the abortive coup to wage an indiscriminate crackdown on dissent. Turkish authorities have suspended, detained or placed under investigation more than 60,000 soldiers, police, judges, teachers, civil servants and others in the past week.

Prime Minister Binali Yildirim said on Saturday authorities had taken around 13,000 people into custody over the coup attempt, including 8,831 soldiers. He pledged they would have a fair trial.

Rights group Amnesty International said it had received credible evidence of detainees being subjected to beatings and torture, including rape, since the coup attempt.

"It is absolutely imperative that the Turkish authorities halt these abhorrent practices and allow international monitors to visit all these detainees in the places they are being held," said Amnesty's Europe director John Dalhuisen in a statement.

Erdogan has extended the maximum period of detention for suspects from four days to 30, a move Amnesty said increased the risk of torture or other maltreatment of detainees.

But for now, the crackdown appears to be broadly popular.

"The state of emergency is a good thing and it's good that many people have been arrested and that the length of detentions has been extended," said demonstrator Harun Kalyancu, 34, a furniture designer and supporter of the ruling party. "If people lost their jobs they must be guilty."

Zuhal Tolbert, 56, who is retired, said the government should be more inclusive.

"The government has to think about the mistakes they have made they have to think about the other half of the population. (who did not vote for them)," she said. "We all have to come together."

SHOW OF UNITY

Erdogan has accused U.S.-based Muslim cleric Fethullah Gulen, who has many followers in Turkey, of masterminding the abortive coup. In his first decree Erdogan ordered the closure of thousands of private schools, charities and foundations with suspected links to Gulen, who denies involvement in the coup.

The CHP and other political parties swiftly joined the ruling Islamist-rooted AKP in condemning the coup attempt, mindful of four other military interventions in Turkey in the past 60 years. The last full-scale coup in 1980 led to mass arrests of politicians and others, torture and executions.

Taksim Square, like much of Istanbul and other cities, is awash with Turkish flags and CHP supporters were also carrying pictures of their hero Kemal Ataturk, the soldier who founded the secular republic on the ashes of the Ottoman Empire in 1923.

Supporters of Erdogan's AKP, which has ruled Turkey since 2002, have generally tended to use religious symbols and rhetoric. But the coup has united both sides in a blaze of nationalist fervour. Istanbul's AKP mayor, Kadir Toptas, has provided free public transport for the rally.

Opposition parties have mixed backing for purging coup supporters with calls for reconciliation and restraint.

"Turkey should completely be purified from the rule of the putsch," said a "Taksim Declaration" issued by the CHP's Kilicdaroglu. "The state should not be governed by anger and revenge. The culprits of the putsch should be tried lawfully with the understanding of abiding by the rule of law," it added.

Turkey's Supreme Military Council (YAS) will meet under Erdogan's supervision on July 28. Erdogan told Reuters in an interview on Thursday that he would restructure the armed forces and bring in "fresh blood".

After the coup, Western countries pledged support for democracy in Turkey, but have also expressed concern over the scale of subsequent purges of state institutions. – Reuters