DUBAI- Saudi Arabia, Egypt, the United Arab Emirates and Bahrain severed their ties with Qatar on Monday, accusing the wealthy Gulf Arab state of supporting terrorism.
Hours later Yemen's state news agency announced that San'aa also decided to cut diplomatic relations. The Maldives also followed suit, saying it was severing diplomatic ties with Qatar.
The coordinated move dramatically escalates a simmering dispute over Qatar's support of the Muslim Brotherhood, the world's oldest Islamist movement, and adds accusations that Doha even backs the agenda of regional arch-rival Iran.
The three Gulf states announced the closure of transport ties with Qatar and gave Qatari visitors and residents two weeks to leave their countries.
Saudi Arabia accused Qatar of backing militant groups and spreading their violent ideology, in an apparent reference to its influential state-owned satellite channel al Jazeera.
"(Qatar) embraces multiple terrorist and sectarian groups aimed at disturbing stability in the region, including the Muslim Brotherhood, ISIS (Islamic State) and al-Qaeda, and promotes the message and schemes of these groups through their media constantly," state news agency SPA said.
The statement went on to accuse Qatar of supporting what it described as Iranian-backed militants in its restive and largely Shi'ite Muslim-populated Eastern region of Qatif and in Bahrain.
On its state news agency, Egypt, the Arab world's most populous nation, said Qatar's policy "threatens Arab national security and sows the seeds of strife and division within Arab societies according to a deliberate plan aimed at the unity and interests of the Arab nation."
In response, Qatar said it regretted the decision and denied the allegations.
"The measures are unjustified and are based on claims and allegations that have no basis in fact," Al-Jazeera quoted the foreign ministry as saying.
Qatar said the decisions would "not affect the normal lives of citizens and residents".
A senior Iranian official said the decision 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.
A split between Doha and its closest allies can have repercussions around the Middle East, where Gulf states have used their financial and political power to influence events in Libya, Egypt, Syria, Iraq and Yemen.
The diplomatic broadside threatens the international prestige of Qatar, which hosts a large U.S. military base and is set to host the 2022 World Cup. It has for years presented itself as a mediator and power broker for the region's many disputes.