A recent surge in cases of Middle East Respiratory Syndrome (MERS), a sometimes deadly virus, in Saudi Arabia has ebbed in the run-up to Islam's annual haj pilgrimage, the kingdom's Health Minister Khaled al-Falih said on Thursday.

As pilgrims poured into Mecca from around the world, the Health Ministry said it had confirmed two more cases of the disease in Riyadh on Thursday, but the number of cases has declined since last month, Falih said.

Most medical staffers touring hospitals and medical centres around Mecca on Wednesday covered their noses and mouths with masks, as did traffic policemen and army personnel deployed to secure the flow of busses carrying pilgrims into the holy city.

"With the help of God and then with the measures taken by the ministry of health we hope to prevent the virus from getting to the pilgrims," said Falih in a news conference.

So far around 1.2 million Muslims have arrived in the kingdom for haj.

In past years it has drawn up to 3 million pilgrims, but authorities have limited numbers in the past two years because of construction work around the Grand Mosque.

Saudi Arabia has banned the slaughter of camels around the holy cities during the pilgrimage. The animals have been found to carry the virus and scientists say they are the most likely source of primary infections of people.

Seven people in the city of Medina who have been infected by MERS have been moved to Riyadh as a precaution to avoid any spread of the disease near the pilgrimage sites, Falih said.

"The spread has begun to shrink and we are optimistic the days of spreading are gone and are behind us," said Falih.

The kingdom has mobilised 25,000 medical staff from different cities into Mecca for the haj season.

(Editing By Angus McDowall)