A dense sandstorm engulfing parts of the Middle East left at least two people dead in Lebanon and hundreds suffering from respiratory problems on Tuesday, as officials warned residents to stay indoors.

Large parts of Lebanon, Syria, Israel and Cyprus were shrouded in a thick cloud of dust from the storm that began sweeping into the region on Monday.

In Syria, the storm cut visibility for government warplanes and helicopters, which carried out many fewer strikes than usual, a monitor said.

Among those worst affected were Syrian refugees living in official and informal camps, particularly in Lebanon.

The Lebanese health ministry said two women had died at hospitals in the Bekaa Valley region because of the storm, without specifying their nationality.

"The number of cases of choking and shortness of breath caused by the sandstorm has risen to 750," the ministry said.

Police distributed face masks on city streets as authorities warned people suffering from health problems, the elderly and pregnant women to stay indoors.

The storm was felt particularly in Lebanon's dozens of informal camps where hundreds of thousands of Syrian refugees live with limited shelter.

In the Bekaa region, a woman wrapped her headscarf over her mouth as she walked by a makeshift tent in one camp.

Lebanon's weather service said the storm was expected to abate from Wednesday night.

Mouin Hamzeh, secretary general of Lebanon's governmental National Council for Scientific Research, said satellite images "clearly show that the sandstorm came from northern Iraq in the direction of central and northern Lebanon, north and east Syria, and southern Turkey."

"It usually happens twice or even three times a year in Lebanon but during spring, March and April, and the unusual thing today is the density of the storm," he told AFP.

In neighbouring Syria, the storm also swept across much of the country, reducing visibility everywhere from coastal Latakia province to eastern Deir Ezzor.

- Storm impedes Syria strikes -

In the city of Mayadeen in Deir Ezzor, several hospitals were no longer receiving patients suffering respiratory problems after running out of oxygen tanks, said the Syrian Observatory for Human Rights, a monitoring group.

Syria's health minister urged citizens to "avoid prolonged exposure to the outdoors" and said hundreds of people had been treated for cases of asthma and other respiratory problems.

The dust cut visibility for government aircraft, which carried out relatively few strikes during the storm, the Syrian Observatory for Human Rights monitor said.

"The sandstorm has paralysed regime airplanes, there were only a few strikes in Damascus province," said Observatory chief Rami Abdel Rahman.

Thick haze was hanging over Jerusalem and much of Israel and the Palestinian Territories, with officials also warning the vulnerable to stay indoors.

The view from the Mount of Olives -- which normally offers a sweeping panorama of Jerusalem's Old City and the Al-Aqsa mosque compound with its golden Dome of the Rock -- was completely obscured by the dust.

The thick cloud also enveloped parts of the eastern Mediterranean island of Cyprus, where residents were told to limit their time outdoors.

Health officials warned that the concentration of dust particles in the air was many times above normal levels.

Several flights were diverted from the coastal airport of Larnaca as visibility dropped to 500 metres (yards).

The island was also suffering from a heatwave, with inland temperatures hitting 41 degrees Celsius (106 degrees Fahrenheit).

The interior ministry said that dozens of Syrian refugees who had been rescued from a fishing boat off the coast of Cyprus on Sunday had been moved from a makeshift camp to a better-equipped facility because of the extreme weather.

The effects of the storm had also reached Cairo, where the city skyline was obscured by a thick haze.

Wahid Saudi, a top official at Egypt's weather authority, said the dust had blown in from the eastern Mediterranean region and was expected to clear after several hours.

burs-sah/mm