The Qatari authorities have accused Saudi Arabia of jeopardising the annual hajj pilgrimage to Mecca of Qatari pilgrims by refusing to guarantee their safety.
Saudi Arabia and its allies have been boycotting Qatar since June 5, accusing it of backing extremist groups and of ties to Shiite Iran, in the region's worst diplomatic crisis in years.
On July 20, Riyadh said that Qataris wanting to perform this year's hajj would be allowed to enter the kingdom for the pilgrimage, but imposed certain restrictions.
The Saudi hajj ministry said Qatari pilgrims arriving by plane must use airlines in agreement with Riyadh.
They would also need to get visas on arrival in Jeddah or Medina, their sole points of entry in the kingdom.
The Qatari Islamic affairs ministry, in a statement published by the official QNA news agency on Sunday, said the Saudi side had "refused to communicate regarding securing the pilgrims safety and facilitating their Hajj".
The ministry accused Riyadh of "intertwining politics with one of the pillars of Islam, which may result in depriving many Muslims from performing this holy obligation".
According to the statement, 20,000 Qatari citizens have registered to take part this year. The ministry said it denied Saudi claims that Doha had suspended those registrations.
Some Gulf media claimed the Qatari statement was a call for the "internationalisation" of the management of the hajj season, which is run by the Saudi authorities.
"Any call to internationalise (the management of) hajj is an aggressive act and a declaration of war," Saudi Foreign Minister Adel al-Jubeir told Arabiya news channel on Sunday.
But Qatari Foreign Minister Sheikh Mohammed bin Abdulrahman al-Thani described the claims as "media fabrications."
"There has not been a single statement by a Qatari official concerning the internationalisation of hajj," he told Al-Jazeera news channel.
Saudi Arabia and its allies Bahrain, Egypt and the United Arab Emirates cut diplomatic ties and imposed sanctions on Doha in June, including the closure of their airspace to Qatari airlines.
The four Arab states accuse Qatar of supporting extremists and of growing too close to Shiite-dominated Iran, the regional arch-rival of Sunni-ruled Saudi Arabia.
Qatar denies the allegations and accuses the Saudi-led bloc of imposing a "siege" on the tiny emirate.
Nearly 90,000 Iranians are expected to attend the hajj in Mecca this year, and were due to start arriving on Sunday, after Tehran boycotted the pilgrimage last year amid tensions with Saudi Arabia.
Iran boycotted the hajj last year after hundreds of people, many of them Iranians, died in a crush at the pilgrimage in Saudi Arabia in 2015, and following a diplomatic rift between the two countries who are vying for power and influence in the region.
In a speech to haj organisers on Sunday, Iranian Supreme Leader Ayatollah Ali Khamenei said that Iranians would never forget the “catastrophic events” of 2015 and called on Saudi Arabia to ensure the security of all pilgrims.