JAKARTA - INDONESIA has sent hundreds of firefighters to battle blazes on Sumatra island that have enveloped Singapore and Malaysia in a choking haze, senior officials said on Friday.

Dozens of fires were still burning across Sumatra on Thursday - many lit by small landholders to clear trees from areas of peatland in order to grow oil palm or other crops.

Indonesia's forest fire chief Noor Hidayat said about 300 extra firefighters had been sent to the worst-affected area, Sumatra's Riau province, which lies opposite Singapore across the Malacca Strait.

'We have been making efforts to contain the fires. It's very difficult in the peatland areas,' Forestry Minister Zulkilfi Hasan told reporters.

Singapore Foreign Minister George Yeo telephoned his Indonesian counterpart Marty Natalegawa on Friday to express the city state's concerns about severe air pollution, and offer help in controlling the fires.

Mr Natalegawa 'assured minister Yeo that Indonesia would address the haze problem, adding that many Indonesians in Sumatra are also affected,' the Singapore foreign ministry statement said.

300 sent to fight hotspots