The US has lost its role as mediator in the Middle East by moving its embassy in Israel to Jerusalem, Turkish President Recep Tayyip Erdogan said in London on Monday.
"With its latest step, America has chosen to be a part of the problem, not a solution, and lost its mediator role in the Middle East peace process," Erdogan told the Chatham House international affairs think tank.
Moving the embassy from Tel Aviv to Jerusalem was "very, very unfortunate," he said, warning it would "increase tensions and ignite an even greater fire between communities". His remarks came as violent clashes erupted along Gaza's border ahead of the controversial embassy opening, leaving 37 Palestinians dead and hundreds wounded in the conflict's bloodiest day in years.
Erdogan urged the international community to "take swift action to put an end to Israel's increasing aggression," denouncing the embassy move as violating international law and UN resolutions.
Jerusalem is one of the most thorny issues of the Israeli-Palestinian conflict, with both sides claiming it as their capital.
Most of the international community does not formally recognise Jerusalem as Israel's capital, and almost all embassies are located in Tel Aviv.
"The establishment of an independent Palestinian state with Jerusalem as its capital is the only way for lasting peace and stability," the Turkish leader said.
By the time the ceremony to inaugurate the embassy began, the clashes had been raging for more than five hours.
- Red carpet for Erdogan -
Erdogan was also deeply critical of US President Donald Trump's decision this month to withdraw Washington from the Iran nuclear deal.
"The nuclear deal is a significant development which should be preserved," Erdogan said, adding that political dialogue with Iran was "beneficial" to the international community.
Turning to Turkey's decades-long efforts to join the European Union, Erdogan said it remained a strategic goal for Ankara but he condemned the "politicisation" of the process.
Erdogan began a three-day visit to Britain on Sunday, with London rolling out the red carpet as it seeks to bolster future trade ties after leaving the European Union next year.
He will meet Queen Elizabeth II on Tuesday -- an audience that has proved relatively uncontroversial compared to the prospect of her meeting Trump.
As he spoke, a group of Kurdish activists protested outside, with further demonstrations expected near Downing Street on Tuesday by media rights group, Reporters Without Borders.
Erdogan's visit comes just weeks before Turkey holds early parliamentary and presidential elections on June 24.
Erdogan, who has dominated Turkey's political scene for the past 15 years, is seeking to reinforce his authority as Turkey moves to a new presidential system of government with expanded powers.
Earlier on Monday, he met three footballers from Turkey or of Turkish origin who play in the Premier League -- Cenk Tosun, Mesut Ozil and Ilkay Gundogan, state-run news agency Anadolu reported.