The Government will do all it can, within the limits of international law, to safeguard the safety and security of citizens in the ongoing haze crisis, Foreign Minister K. Shanmugam said on Saturday.

The primary duty is to ensure Singaporeans' health and well-being, he said, adding: "There are limitations (in international law) but we will take all steps even if it means that our neighbours are upset."

Actions by countries which have an environmental impact on other nations are "not consistent" with international law, he noted, but ultimately a country's sovereignty was supreme.

As the Pollutant Standards Index breached the hazardous range for a fourth consecutive day, Mr Shanmugam, who is also Law Minister, said he will take up the haze issue with Indonesia during an Asean meeting in Brunei next week.

Ms Grace Fu, the Second Minister for the Environment and Water Resources, and Foreign Affairs, will accompany Mr Shanmugam.

In a briefing with reporters at the Ministry of Foreign Affairs, he also said that Singapore had offered assistance at all levels, from aircraft to manpower, to Indonesia to combat the haze.

But unlike in 2005 when the Indonesians accepted assistance from Singapore, the current offer has yet to be taken up.

Some Singapore firms have also been linked with the burning of land in Riau that is contributing to the haze, and the minister said the Attorney-General's Chambers is checking on what powers the Singapore Government has in dealing with these companies.