The move comes days after Saudi Arabia announced a breakthrough in ending the three-and-half-year Gulf dispute.
Vehicles have crossed the Saudi Arabian land border from Qatar for the first time since four Arab states severed diplomatic and transport ties with Doha in mid-2017.
The development came on Saturday after a deal this week to restore relations between the Gulf neighbours.
“Yes, the border is open,” one Qatari source told AFP news agency, while another confirmed that traffic at the Abu Samra crossing, 120km (75 miles) south of Doha, resumed about 07:00 GMT.
— عبدالله الوذين (@abqatar) January 9, 2021
“It’s good the crisis has been resolved and the warm welcome we had, and the happiness we see in our brothers,” the driver of the second car to pass through the crossing told the kingdom’s Ekhbariya TV.
Zaid Muhammad al-Marri, 23, a Qatari whose mother is Saudi, said: “It is a great joy, I bought this new car, a Land Cruiser, in order to go and celebrate with my relatives in Saudi Arabia, and I took the coronavirus test and waited here hoping they would allow us to cross at any moment.”
Riyadh on Tuesday announced a US-backed deal to end a bitter dispute with Qatar that saw Saudi Arabia, the United Arab Emirates (UAE), Bahrain and Egypt impose an embargo on Doha over allegations that it supports “extremism” and Iran. Qatar denies the charges and says the boycott aimed at curtailing its sovereignty.
A UAE official this week said travel and trade links could resume within a week of the deal, but restoring diplomatic ties requires more time as parties work to rebuild trust.
So far, no flights have resumed between Qatar and the four Arab states. Qatar Airways on Thursday began rerouting some of its flights through Saudi airspace.
Etihad Airways, Abu Dhabi’s carrier, intends to recommence services between Abu Dhabi and Doha, a spokesperson said on Saturday.
Measures to contain the spread of the new coronavirus are in place on both sides of the Saudi-Qatar land border.
All arrivals into Qatar crossing at Abu Samra must present a negative COVID-19 test, take a new test at the border and quarantine for one week in one of a number of selected hotels, Qatar News Agency said.