Arab countries' decisions led by Saudi Arabia are founded on 'baseless' allegations, Qatar foreign ministry says.
Qatar said there is "no legitimate justification" for several nations cutting diplomatic ties after Saudi Arabia, Egypt, UAE, Bahrain, Yemen and the Maldives announced they would suspend relations with the Gulf state.
The Saudi kingdom made the announcement via its state-run Saudi Press Agency early on Monday, saying it was taking action for what it called the protection of national security.
The news agency released a statement in which it accused Qatar of "harbouring a multitude of terrorist and sectarian groups that aim to create instability in the region".
Reacting to the fallout, Qatar explained that the decision was in "violation of its sovereignty," vowing to its citizens and the hundreds of thousands of residents that the measures would not affect them.
"The measures are unjustified and are based on claims and allegations that have no basis in fact," the statement said, adding that the decisions would "not affect the normal lives of citizens and residents".
"The aim is clear, and it is to impose guardianship on the state. This by itself is a violation of its (Qatar's) sovereignty as a state," it added.
Qatar's foreign ministry made the statement hours after the Saudi announcement, but before Yemen's internationally backed government, which no longer holds its capital and large portions of the country.
Libya's out of mandate Prime Minister Abdullah al-Thinni later joined the Arab nations in saying they too would cut ties.
As part of the measures, Saudi Arabia said it would pull Qatari support from the Yemen war.
Airspace and sea traffic would also be affected, with major Saudi and UAE-based airlines announcing they would stop flying to the Qatari capital, Doha.
Etihad Airways, the UAE's national carrier, said it would suspend flights to and from Qatar starting Tuesday. Emirates, a Dubai-based airline, and FlyDubai, the emirate's budget airline, quickly followed suit.
It was unclear how other airlines would react.
Saudi Arabia had called on "brotherly" countries to join its measures against Qatar.
The UAE said in a statement it was cutting off all ties with Qatar. It also ordered Qatari citizens to leave te country within 14 days and banned its citizens from travelling to Qatar.
Later on Monday, the Qatari embassy in Abu Dhabi asked citizens to leave the UAE within 14 days.
"Qatari citizens must leave the UAE within 14 days, in accordance with the statement issued by the concerned Emirati parties," the embassy said in a tweet, adding that those who cannot travel directly to Doha should go through Kuwait or Oman.
Bahrain's foreign ministry issued a statement saying it would withdraw its diplomatic mission from Doha within 48 hours and that all Qatari diplomats should leave Bahrain within the same period.
Egypt also announced the closure of its airspace and seaports for all Qatari transportation "to protect its national security", the foreign ministry said in a statement.
Later on Monday, the Maldives said in a statement that it took the decision to sever diplomatic ties "because of its firm opposition to activities that encourage terrorism and extremism".
The announcements roiled financial markets, with the price of oil surging and Qatari stocks and shares falling.
"This is the most serious political crisis in the region in years," said Hashem Ahelbarra, Al Jazeera's senior Middle East correspondent. "There are two aspects here, political and economic, to put more pressure on Qatar.
"The official statement here in Qatar is basically that they view [the fallout] as part of coordinated effort to further undermine Qatar.
"It will ultimately have to be solved at the diplomatic level."
US, Iran, Turkey react
US Secretary of State Rex Tillerson gave a statement on Monday while on state visit in Australia, urging the Gulf states to stay united.
"We certainly would encourage the parties to sit down together and address these differences," he said in Sydney.
"If there's any role that we can play in terms of helping them address those, we think it is important that the GCC (Gulf Cooperation Council) remain united."
Tillerson said despite the impasse, he did not expect it to have "any significant impact, if any impact at all, on the unified fight against terrorism in the region or globally".
"All of those parties you mentioned have been quite unified in the fight against terrorism and the fight against Daesh, ISIS, and have expressed that most recently in the summit in Riyadh," he added, using alternative names for the Islamic State of Iraq and the Levant (ISIL) group.
Mevlut Cavusoglu, Turkey's foreign minister, also called for dialogue to resolve the dispute.
"We see the stability in the Gulf region as our own unity and solidarity," Cavusoglu told reporters.
"Countries may of course have some issues, but dialogue must continue under every circumstance for problems to be resolved peacefully. We are saddened by the current picture and will give any support for its normalisation".
A senior Iranian official said the measures by the Arab nations would not help end the crisis in the Middle East.
"The era of cutting diplomatic ties and closing borders ... is not a way to resolve crisis ... As I said before, aggression and occupation will have no result but instability," Hamid Aboutalebi, deputy chief of staff of Iran's President Hassan Rouhani, tweeted, referring to the coalition's involvement in Yemen.
The dispute between Qatar and the Gulf's Arab countries escalated after a recent hack of Qatar's state-run news agency. It has spiralled since.
Following the hacking on Tuesday, comments falsely attributed to Qatar's emir, Sheikh Tamim bin Hamad Al Thani, were broadcast in Qatar.
Qatar's government categorically denied that the comments, in which the country's leader expressed support for Iran, Hamas, Hezbollah and Israel - while suggesting that US President Donald Trump may not last in power, were ever made.
"There are international laws governing such crimes, especially the cyberattack. [The hackers] will be prosecuted according to the law," Mohammed bin Abdulrahman Al Thani, Qatar's foreign minister, said on Wednesday.
UAE-based Sky News Arabia and Al Arabiya kept running the discredited story, despite the Qatari denials.