Egypt's plan to hand over two uninhabited Red Sea islands to Saudi Arabia under an agreement that has attracted widespread criticism moved closer to fruition with parliament set to vote on the measure on Wednesday.

Qatar, the world's second largest helium producer, has closed its two helium production plants because of the economic boycott imposed by other Arab states, industry sources told Reuters on Tuesday.

Egypt will allow airlines and aircraft that are not registered in Egypt or Qatar to use its airspace to fly to and from Qatar, the civil aviation ministry said on Tuesday - an easing of restrictions imposed in a Saudi-led diplomatic isolation of Qatar.

Qatar said on Wednesday it had withdrawn its peacekeeping troops from the disputed frontier between Djibouti and Eritrea, after the two East African countries sided with Saudi Arabia and its allies in their standoff with Qatar.

The U.S. ambassador to Qatar said Tuesday she is leaving her post in Doha, in the midst of the worst diplomatic crisis involving America's Gulf allies in years.

Turkey, a strong ally of Qatar, will send its foreign minister to Doha on Wednesday and then if possible to Saudi Arabia in a diplomatic push to help end a bitter feud between the emirate and a number of other Arab countries.

The United Arab Emirates' ambassador to the United States said on Tuesday there was no military aspect to steps taken by Arab powers against Qatar, which they accuse of supporting terrorism.

Turkish President Tayyip Erdogan on Tuesday denounced the isolation of Qatar by neighboring states as a violation of Islamic values and akin to a "death penalty" imposed in a crisis that has reverberated across the Middle East and beyond.

Saudi Foreign Minister Adel al-Jubeir said his country was ready to provide food and medical aid to Qatar if needed, Sky News Arabia reported, a week after Riyadh and other Arab capitals cut ties with their Gulf neighbor.

Russian President Vladimir Putin and Saudi Arabia's King Salman discussed the Qatar crisis in a phone call on Tuesday, the Kremlin said in a statement.

Morocco said it would send plane-loads of food to Qatar to boost supplies thereafter Gulf Arab states cut diplomatic and economic ties with Doha.

U.S. Defense Secretary Jim Mattis said on Monday that the blockade against Qatar by Gulf states including Saudi Arabia was a "very complex situation" and it was an area where common ground had to be found.

Turkish President Tayyip Erdogan on Tuesday denounced the isolation of Qatar as "inhumane and against Islamic values", and said the methods used against the Gulf state were unacceptable, and analogous to a "death penalty".

The king of Saudi Arabia and the Iraqi prime minister will meet on Wednesday, a Saudi newspaper reported, their second meeting this year as the neighbours try to heal a rift over Iraq's alliance with Saudi arch foe Iran.

Iraq is opposed to the isolation of Qatar by Saudi Arabia and other Gulf Arab neighbours because it hurts ordinary citizens, Iraqi Prime Minister Haider al-Abadi said on Tuesday.

Iranian Foreign Minister Mohammad Javad Zarif said on Tuesday Saudi Arabia was supporting militants inside Iran, days after hardline Sunni group Islamic State claimed attacks in Tehran.

Qatar on Monday denounced the sanctions imposed against Doha by Saudi Arabia and its allies as "unfair" and "illegal", as Britain announced talks to try to resolve the crisis.

Islamic State leader Abu Bakr al-Baghdadi is on the brink of losing the two main centers of his 'caliphate' but even though he is on the run, it may take years to capture or kill him, officials and experts said.

Qatar supports Kuwait's efforts to end a rift with Saudi Arabia and other Arab states, its foreign minister said on Monday, but the emirate remains puzzled over why "abusive measures" had been imposed on it.

Qatar's foreign minister told state-funded broadcaster Al Jazeera on Monday that his country and the United States both remained in touch with the emir of Kuwait.