Saudi Arabia — Qataris celebrated crossing their border with Saudi Arabia on Sunday, calling the kingdom "our second country", as Doha readied its strict coronavirus measures for Saudis to enter following a Gulf diplomatic thaw.

Drivers arrived at the Salwa border crossing in Saudi Arabia, 500 kilometres east of the capital Riyadh, from the Qatari land crossing at Abu Samrah for the second day following its reopening, AFP correspondents reported.

Saudi Arabia shut its side of Qatar's only land border in June 2017 as part of a package of sanctions it said was a response to Doha's backing of radical Islamist groups and closeness to Iran.

Qatar always denied the charges.

Saudi Arabia, along with the United Arab Emirates, Bahrain and Egypt, all of which had also imposed embargoes on travel and trade, agreed to lift the restrictions at a Gulf Cooperation Council summit in the kingdom on Tuesday.

"Coming from Qatar is like coming to our second country, where there's no difference between them and us in their traditions," said Mohammed Al Marri, a Qatari who had travelled into Saudi Arabia.

Since the re-opening of the border, 167 Qatari cars had entered Saudi Arabia, while 35 Qatari vehicles had crossed back into Qatar, said Ali Lablabi, general manager of Salwa's customs department.

"This happiness — no one can describe it," said Ghaith Al Marri, a Qatari. "There are people who started crying" when the border re-opened, he said.

Qatar Airways and Saudi Airlines announced Saturday on Twitter that they would begin resuming flights between their countries from Monday.

Qatar has announced strict coronavirus control measures for those arriving from Saudi Arabia.

Doha will require travellers to present a negative coronavirus test, undergo another test at the frontier and quarantine in a government-approved hotel for one week.

Just one hour from the Salwa border crossing lies Al Ahsa, a desert oasis where Qatari shoppers once kept the local economy humming, crossing over to buy affordable supplies including dates and milk.

The deep-pocketed residents of gas-rich Qatar — one of the world's wealthiest countries per capita — also pumped millions of riyals into Saudi hotels, date plantations and other real estate.

But the money dried up when the embargo shut the Qataris out, unleashing economic pain and dividing extended families on both sides, an unintended consequence of a policy meant to hurt Doha's government.