Turkish Prime Minister Recep Tayyip Erdogan said his government would go ahead with controversial plans to overhaul a small park in central Istanbul, despite mass protests against the redevelopment in Taksim Square.

Speaking to reporters in Tunis after a meeting with his Tunisian counterpart on Thursday, Erdogan said some groups were manipulating what had started as an environmental protest.

"Among the protesters, there are extremists, some of them implicated in terrorism," he told reporters.

Turkish PM also added that those who caused damage as part of the Taksim Gezi Park protests were the same as those who attacked he US embassy in Ankara four months ago, in which one security guard and one attacker were killed. Ecevit Sanli, a member of the outlawed Revolutionary People’s Liberation Party/Front (DHKP/C), conducted the attack.

No outright apology

On the alleged excessive use of force against those protesting, Erdogan did not make an outright apology, and said that "the neccessary words" of regret had already been said by his deputy.

Turkish Deputy Prime Minister Bulent Arinc apologised for the use of excessive force by the police in protests on Tuesday.

"My deputy made the necessary statement and I expressed my sadness over the excessive use of tear gas," said Erdogan, adding that rights can not be acquired by illegal methods.

Al Jazeera's Anita McNaught, reporting from Ankara, said Erdogan also stressed on the amount of vandalism caused by protesters on some infrastructure, saying that it "was scarecely in the name of environmentalism."

Resuming his effort to calm down tension in the country, Turkish President Abdullah Gül called for protesters to “set the streets free.”

However, thousands of anti-government protesters are gathering in Istanbul's Taksim Square ahead of Erdogan's return from a North African tour.

Al Jazeera's Gokhan Yivciger reported earlier that some Turkish artists demanding the government to resign walked to the Gezi Park in the square.

Seven foreign nationals living in Turkey who are accused of helping to provoke the protests are under detention.

Evaluation procedures are continuing into the two Iranian citizens, two French, a Greek, a US citizen and a German, Turkey’s Interior Minister Muammer Güler said on Thursday.

Stocks fall

Turkish assets weakened following Erdogan's latest remarks in Tunisia.

The main Istanbul share index fell over 8 percent, while the lira weakened to 1.90 against the dollar following Erdogan's comments.

The protests in Turkey were sparked early June by the police break-up of a sit-in to prevent the demolition of a park in central Istanbul.

The demonstration spiralled into rallies by thousands denouncing what they say is the government's increasingly authoritarian form of governing and its meddling in people's lifestyles.