A dispute broke between Washington and Ankara after it was revealed that CNN correspondent Ivan Watson had been harassed by Turkish police on the anniversary of Gezi protests.

US State Department officials dismissed Turkish Prime Minister Recep Erdogan's comments that Watson was "an agent" and wanted to "stir up trouble in Turkey".

Department Spokesperson Marie Harf described his accusation as "ridiculous".

The CNN "are nothing except for independent and non-biased media," Harf was quoted by Hurriyet Daily News as saying.

She warned that developments in Turkey "have continued to raise" concerns and that Washintgon was "closely monitoring" official response to demonstrations held a year after the Gezi Park protests.

Over the weekend CNN International reported its correspondent Ivan Watson had been harassed by Turkish plainclothes police in Istanbul while speaking live in the eve of the Gezi Park anniversary.

Watson could be heard as saying to an anchor that he and his crew was "being detained right now". Later he said police officers had demanded his press credentials and had sad it could have been "counterfeited". The team was released in half an hour.

Prime Minister Erdogan lambasted at him by calling him a "CNN International lackey" and also by saying he was a proof "[CNN] have been caught red-handed".

He also put into question the media's independence and impartiality, calling its reporters "agents".

This is not the first time Erdogan has recently embarked on attacks at foreign-based news services or web platforms.

Earlier this spring he vowed to "eradicate" Twitter and was harshly critical of YouTube and Facebook, suggesting the interests they served were dangerous to Turkey and arguing they could be used to incite espionage.

He even ordered a ban on Twitter and YouTube, with the latter finally being accessible this week after having been shut down for two months.