Pilgrims wear protective face masks to prevent contracting coronavirus as they walk outside the Grand Mosque in the Holy City of Makkah. File
The announcement comes amid uncertainty over the Hajj which is due to take place at the end of July, after authorities this week urged Muslims to temporarily defer preparations for the annual pilgrimage.
"Full 24-hour curfew in Makkah and Medina starting from today until further notice," the official Saudi Press Agency reported, citing an interior ministry source.
The cities were earlier under a 15-hour daily curfew.
Authorities have already sealed off Makkah and Medina along with Riyadh and Jeddah, barring people from entering and exiting the cities as well as prohibiting movement between all provinces.
Saudi Arabia, which has reported the highest number of infections in the Gulf, is scrambling to limit the spread of the disease at home.
On Thursday the health ministry said the deaths from the illness had risen to 21 while 1,885 infections were reported.
Last month, Saudi Arabia suspended the year-round "Umrah" pilgrimage over fears of the coronavirus pandemic spreading to Islam's holiest cities.
Authorities are yet to announce whether they will proceed with this year's Hajj.
The Arab world's biggest economy has also closed down cinemas, malls, restaurants and halted flights as it steps up efforts to contain the virus.
The state-run Saudi Press Agency cited Saleh Bin Taher Banten's remarks in stories early on Wednesday, saying that Muslims should "be patient” in making their plans for the Hajj. The pilgrimage was expected to begin in late July this year.
The decision also affected travel to Prophet Muhammad's (PBUH) mosque in Medina. Authorities also suspended entry to the kingdom to those with tourist visas from nations affected by the new virus.
Saudi Arabia will enforce a 24-hour curfew across the kingdom during a 5-day holiday to celebrate Eid Al Fitr which marks the end of the Holy Month of Ramadan, the interior ministry said in a statement on Tuesday, to stem the spread of coronavirus.
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