Indonesia President Susilo Bambang Yudhoyono apologized Monday as skylines in neighboring Singapore and Malaysia remained enveloped in thick haze caused by forest fires in Sumatra.

“I, as the president, apologize and seek the understanding of our brothers and sisters in Singapore and Malaysia,” Yudhoyono told a news conference. “Indonesia had no intention to cause this.”

He said dry weather conditions had worsened the problem and that he thought the local government in Riau province, where most of the fires are blazing, was late in anticipating the grave impact, reports Wall Street Journal.

The Indonesian leader also pledged to “focus on tackling these fires immediately.”

The smoke triggered by slash-and-burn farming techniques for palm-oil plantations has ratcheted up pollution levels in Malaysia’s south where schools were forced to shut down and hospitals scrambled to accommodate the increasing number of patients complaining of eye and respiratory problems.

In Singapore, the air pollution index reached records last week before subsiding over the weekend as the smoke blew towards Kuala Lumpur.

Some of the world’s largest palm-oil companies on Monday denied involvement in setting the fires. Singapore’s Wilmar International Ltd., Malaysia-listed Sime Darby Bhd. and Kuala Lumpur Kepong Bhd. issued statements saying they have strict “zero-burning policy”, according to the Journal.