Turkey has been urged to investigate whether police used excessive force in a crackdown on days of anti-government demonstrations and hold those responsible to account.

European Union enlargement commissioner Stefan Fuele said: "Peaceful demonstrations constitute a legitimate way for ... groups to express their views in a democratic society.

"Excessive use of force by police against these demonstrations has no place in such a democracy”.

Mr Fuele was speaking at a conference attended by Turkish Prime Minister Recep Tayyip Erdogan.

"I am happy that even the government admitted that. What is important now, is not only to launch a swift and transparent investigation but also to bring those responsible to account," the EU commissioner said.

It comes after Mr Erdogan told thousands of cheering supporters that his authority came from the ballot box and urged them not to be drawn into violence.

Addressing crowds at Istanbul airport from an open-top bus after returning from a trip to North Africa, Mr Erdogan called on his ruling party faithful to show restraint.

He said they should distance themselves from "dirty games" and "lawless protests".

Turkey has been rocked by its worst political unrest for decades over the past week, with anti-government riots challenging Mr Erdogan's authority.

The protests have damaged the country's image abroad and highlighted concerns about human rights and freedom of speech in the EU candidate nation.

"We stood strong, but we were never stubborn ... We are together, we are unified, we are brothers," Mr Erdogan told his supporters.

"Some people say, 'The prime minister is only prime minister to 50%'. We have always said that we are the servants of 76 million," he said, as the crowds chanted his name.

What began as a campaign against planned construction on a park in a corner of Istanbul's Taksim Square has grown into an unprecedented display of public anger over the perceived authoritarianism of Mr Erdogan and his Islamist-rooted AK Party.

Police backed by armoured vehicles and helicopters have clashed with groups of protesters night after night, leaving three dead and 4,000 injured.

Thousands of Mr Erdogan's opponents have massed peacefully in Taksim, surrounded by barricades of torn-up paving stones and street signs.

They gathered again ahead of Mr Erdogan's return.

Some of the demonstrators in Taksim chanted "Tayyip resign", while others sang and danced. In Ankara's Kugulu Park, thousands chanted anti-government slogans and sang the national anthem.

But Mr Erdogan has so far struck a defiant tone.

Speaking in Tunis he condemned the "burn and destroy" tactics of some of those involved in the protests, and promised to press ahead with the plans for Taksim that triggered the unrest.

He said that "terror groups", including one that claimed responsibility for a 1 February bombing at the US Embassy in Ankara, were manipulating the crowds.

Mr Erdogan struck a firm but arguably more conciliatory tone at the airport, clearly playing to the gallery, but also acknowledging accusations of excessive police force and pledging to work to foster unity in the wake of the protests.

"We have not marginalised anyone's beliefs ... We are Turkey together, we are brothers. We will evaluate everything that has taken place in Turkey and based on that take a step," he said.

"The secret to our success is not tension and polarisation."

The protesters have a variety of political backgrounds, including far leftists, nationalists, environmentalists and secular Turks.

Their numbers at Taksim have swollen at points to more than an estimated 100,000.