Bahrain accused Iran on Thursday of "biological aggression" by covering up the spread of the new coronavirus and failing to stamp the passports of Bahraini travellers, as other Gulf Arab states boosted measures to stem rising infections.
Iran, epicentre of the flu-like disease in the Middle East, saw its caseload grow by 1,075 to more than 10,000, while its death toll reached 429.
Many of the recorded infections throughout the Gulf region are linked to travel to Iran, which hosts several important shrines and pilgrimage sites for Shi'ite Muslims. No Gulf Arab state has so far reported a coronavirus death.
"With this behaviour, Iran has allowed the disease to travel abroad, and in my estimation this constitutes a form of biological aggression that is criminalised by international law, as it has put in danger our safety and health and that of others," Bahraini Interior Minister General Sheikh Rashid bin Abdulla Al Khalifa said in comments on Twitter.
Bahrain on Wednesday reported 77 new infections among citizens evacuated from Iran. A second government-chartered repatriation flight is scheduled for Thursday.
In an apparent response to Al Khalifa's comments, special aide to Iran's parliament speaker Amir Abdollahian tweeted: "America, which rules Bahrain through the presence of its Fifth Fleet, is a major cause of biological warfare and initially denied the existence of coronavirus."
Saudi Arabia, which has a minority Shi'ite population and had previously criminialised travel to Iran, last week denounced its key regional rival for granting Saudi citizens entry amid the outbreak. Bahrain, where Shi'ites make up a majority of the population, has no such restrictions.
Iranian Foreign Ministry spokesman Abbas Mousavi has denied that not stamping passports has anything to do with coronavirus and called on Riyadh to avoid politicising the epidemic.
"...Attaching labels and issuing entry and exit stamps (in the passports) is avoided, in conformity with the visa policy of many advanced countries," he said on Tuesday.
Bahrain said separately on Thursday that non-compliance with isolation measures would be punishable by up to three months in jail and a fine of up to 10,000 Kuwaiti dinars ($32,000). Three individuals have already been reported to the public prosecutor, state news agency BNA reported.
Saudi Arabia, which has suspended the Umrah pilgrimage and locked down its eastern Qatif region where many infections are located, announced 24 new cases overnight, bringing its total to 45.
Riyadh halted flights to the European Union and 12 other countries, extending an earlier ban and giving Saudi citizens and residents 72 hours to return, state news agency SPA said.
The flight ban now includes Switzerland, India, Pakistan, Sri Lanka, the Philippines, Sudan, Ethiopia, South Sudan, Eritrea, Kenya, Djibouti, and Somalia -- countries where millions of migrant workers in Saudi Arabia hail from.
Passenger traffic through all land crossings with Jordan was also suspended. Commercial and cargo traffic continued.
Saudi Arabia's health ministry asked people to avoid handshaking and gatherings of more than 50.
Kuwait reported eight new infections, taking its total to 80, as the country started a two-week public holiday that has been declared to help contain the spread of the virus.
Authorities also shut the stock market on Thursday and banned all commercial passenger flights to and from the country.
Oman introduced a raft of measures to control the virus' spread, including suspending tourist visas from all countries and banning cruise ships from docking.
The neighbouring United Arab Emirates (UAE) said its total number of cases had increased by 11 to 85.
A spokesman for public relations firm Edelman told Reuters an employee had tested positive for coronavirus, and that staff at its UAE offices would work remotely.
Dubai's Emirates airline, one of the world's biggest long-haul carriers, said it was suspending flights to Italy until April 3, in addition to other routes in the United States, Europe and Far East.
Qatar on Wednesday announced 238 new cases among expatriates in a residential compound that had been placed under quarantine after three residents tested positive for the virus on Sunday.