Some people have waited years to make this trip, and permits are allocated by Saudi authorities on a quota basis for each country.
Nonartina Hajipaoli, 50, told AFP she was proud to be among the 1,000 pilgrims from Brunei in Southeast Asia this year.
“I am speechless, I can't describe what I am feeling,” she said.
More than 1.8 million pilgrims attended the hajj last year, after authorities lifted pandemic-era restrictions and abolished age limits, according to official data.
According to official media, by late Monday night, around 15 lakh people had reached for Haj this year.
As has been the case for many years, this year the gathering is taking place during Saudi Arabia's intense summer, with officials predicting an average maximum temperature of 44 degrees Celsius (111 degrees Fahrenheit).
Saudi health ministry spokesman Mohammed al-Abdulali told AFP this week that more than 10,000 cases of heat-related illnesses were recorded last year, 10 percent of them heat stroke.
Mitigation measures this year include misting systems and heat-reflective road coverings.
A message sent to pilgrims on Thursday instructed them to “drink water regularly, more than 2 litres per day” and “always carry an umbrella”, warning that temperatures could rise to 48 degrees Celsius.