Most of Nigeria was shrouded in a thick dust storm Wednesday, disrupting air travel and threatening to trigger respiratory problems, officials said.

Experts said that climate change may be responsible for the severity and abnormal timing of the storm. Normally milder dust storms arrive between November and February when seasonal winds blow sand down from the Sahara desert.

"That this is happening in March is unusual and because of its severity, it is causing concerns among the people," senior weather forecaster Samson Wilson told AFP.

He said the skies were expected to clear and the weather was due to return to normal in the coming few days.

The dust storm first hit the northern part of last week before sweeping southwards at the weekend.

The Nigerian Airspace Management Agency said it has cancelled flights due to poor visibility.

"We have had cause to suspend or cancel some flights because of poor visibility," NAMA spokesman Supo Atobatele told AFP.

Wilson said the excess amounts of dust particles in the air could cause respiratory ailments.