Lewa Pardomuan, Jakarta – Thick smog from rampant forest and bush fires spread to more cities in Indonesia on Sunday while uncertainties over the start of the annual monsoon rains lingered, meteorologists said.

They said the number of cities covered by the smog had nearly doubled to 41 from 22 as of Sunday morning, while at least four airports were closed due to poor visibility.

The smog is blanketing large parts of Sumatra island, the Kalimantan region on the Indonesian side of Borneo island and the remote province of Irian Jaya.

"Many more cities are covered by the smog. We have reports of two cities in Sumatra which have zero visibility," said an official at Jakarta's National Meteorology Bureau.

"There were some rains on Saturday in west Java and parts of Irian, but they were localised," he said.

U.N. climate experts in Geneva said on Friday that the dry spell in Indonesia could continue for three months – far beyond the normal start of the monsoon – due to the El Nino phenomenon, a periodic upswelling of warm water in the Pacific Ocean which affects global weather patterns.

Dense smoke from forest fires on Sumatra island and in Kalimantan, particularly from huge deposits of burning peat spewing carbon into the air, has spread a choking smog over large areas of Southeast Asia.

Indonesian meteorologists have said dry winds from Australia are still dominant and that wind patterns have delayed the possibility of widespread rains in the archipelago.

The annual rains normally start in September, with full monsoon rains the following month. Scattered rain has fallen so far this season while drought conditions prevail through much of the archipelago stretching 5,000 km (3,000 miles) along the equator.

The drought has also been blamed for more than 460 deaths from famine and disease among tribes in the remote, rugged jungles of Irian Jaya, where relief workers are flying in emergency supplies and medicines.

Residents in Jambi, on Sumatra island, said thick smog still blanketed the city. "Actually, the situation is a little bit better, maybe because of some rains last night," said one resident. "But still, we cannot see the sun because smog has blocked it. People are wearing masks when outside their homes," he said.

Officials at the forest fire control bureau in Jakarta said they recorded nine "hot spots" in Sumatra and Kalimantan, but added it did not necessarily meant the number of areas had subsided.

"Not all areas can be photographed by the satellite because they could be covered by smog," said one official.

Kompas newspaper reported on Sunday the drought had triggered a severe water shortage in a number of villages in East Java, which forced local people to buy fresh water for their daily needs.

Residents said they did not have enough money to buy water because the drought had destroyed their crops.

Agriculture ministry officials say the drought will affect production of key commodities in Indonesia such as rice, coffee, tea, cocoa and palm oil.

Political sources say authorities are also keeping a wary eye out for possible food riots, although officials say rice stocks are enough to see the country through the drought.

The smog has triggered alarms in Singapore, Malaysia and Brunei and has spread as far as the Philippines and Thailand.