Islamic leaders on Wednesday urged world powers to recognise occupied East Jerusalem as the capital of the "State of Palestine", as Palestinian president Mahmoud Abbas warned that the United States no longer had a role to play in the peace process.

Turkish President Recep Tayyip Erdogan convened an emergency summit of the world's main pan-Islamic body, the Organisation of Islamic Cooperation (OIC), in Istanbul, seeking a tough response to the recognition by US President Donald Trump of Jerusalem as Israel's capital.

With the Islamic world itself mired in division, the summit fell well short of agreeing any concrete sanction against Israel or the United States.

But their final statement declared "East Jerusalem as the capital of the State of Palestine" and invited "all countries to recognise the State of Palestine and East Jerusalem as its occupied capital."

- 'Null and void -

They declared Trump's decision "null and void legally" and "a deliberate undermining of all peace efforts" that would give impetus to "extremism and terrorism".

The status of Jerusalem, a city considered holy by Christians, Jews and Muslims, is perhaps the most sensitive issue in the Israeli-Palestinian conflict.

Israel sees the entire city as its undivided capital, while the Palestinians want the eastern sector, which the international community regards as annexed by Israel, as the capital of their future state.

Israeli Prime Minister Benjamin Netanyahu said in response that he was "not impressed" by the OIC statements.

"The Palestinians would do better by recognising reality and acting in favour of peace and not extremism," Netanyahu said.

Erdogan, who sees himself a champion of the Palestinian cause, sought to underline his point with a powerpoint map presentation, flashing a laser pointer at how Palestinian territory had shrunk since the 1948 creation of Israel.

"The real proprietor of these lands is Palestine," he said.

"Mr Trump wants all this to be Israel. This is the product of an evangelist and Zionist mentality," said Erdogan, the current OIC chairman.

- 'No more role for US' -

Using unusually strong language and bitterly anti-American rhetoric, Abbas warned that there could be "no peace or stability" in the Middle East until Jerusalem is recognised as the capital of a Palestinian state.

He added that Trump's move had withdrawn the United States from its traditional role as Mideast peace mediator.

"We do not accept any role of the United States in the political process from now on. Because it is completely biased towards Israel," he said.

The final OIC statement echoed his words, saying Trump's move was "an announcement of the US administration's withdrawal from its role as sponsor of peace".

Successive US administrations have sought unsuccessfully to broker a final peace deal since the 1990s Oslo accords. Trump, too, is working on such an offer through his son-in-law Jared Kushner.

- Saudi snub? -

But bridging the gaps between 57 OIC member states -- which include archrivals Sunni Saudi Arabia and Shiite Iran -- was always a tall order.

Key players, like Egypt, Saudi Arabia and the United Arab Emirates, were unlikely to want to risk their key relationship with Washington by putting their name to anti-American measures.

Iranian President Hassan Rouhani, Jordanian King Abdullah II and Lebanese President Michel Aoun were among the heads of state present, as well as the emirs of Qatar and Kuwait and presidents of Afghanistan and Indonesia.

But there was no sign of Saudi King Salman or his powerful crown prince and son Mohammed bin Salman, who has reportedly been in close contact with Trump over the Middle East. Instead, Riyadh sent a senior foreign ministry official.

"Some countries in our region are in cooperation with the United States and the Zionist regime and determining the fate of Palestine," seethed Rouhani, whose country does not recognise Israel.

But as the summit was being held, King Salman echoed the calls over Jerusalem in an address in Riyadh, saying it was the "right" of the Palestinians to establish "their independent state with East Jerusalem as its capital".

Sudanese President Omar al-Bashir, who is wanted by the International Criminal Court for genocide and war crimes, was also in attendance and warmly greeted by Erdogan.

A surprise guest was Venezuela's leftist President Nicolas Maduro, whose country has no significant Muslim population but is a bitter critic of US policy.

Trump's announcement last week prompted an outpouring of anger in the Muslim and Arab world, where tens of thousands of people took to the streets to denounce Israel and show solidarity with Palestinians.

The decision sparked protests in Palestinian territories, with four Palestinians killed so far in clashes or Israeli air strikes in response to rocket fire from Gaza and hundreds wounded.