Indonesia has extended legal protection for its wetlands and peat bogs by expanding a ban on the conversion of these carbon-rich swamps into plantations.

The move, if properly enforced, could drastically reduce Indonesia's sizeable carbon footprint and prevent a repeat of the annual forest fires that plague the region, conservationists say.

A moratorium on new conversions of certain peatland areas has been in place since 2011 in Indonesia.

But this latest revision -- signed into law by President Joko Widodo, and issued Monday -- clarifies and expands the law, ensuring that all peatlands are covered and that companies must restore areas they have degraded.

"We want to avoid any misinterpretation of the existing regulation, which gives the impression that land-clearing is still allowed," environment ministry spokesman Djati Witjaksono Hadi told AFP Tuesday.

Peatlands take thousands of years to form as layers of dense wet plant material compact into dense carbon stores.

When these ancient swamps are drained or cleared by fire to make way for commercial plantations -- such as for palm oil or pulp wood -- that carbon is released into the atmosphere.

Conservationists hailed the strengthened moratorium as a win for climate change.

"This regulation will be a major contribution to the Paris climate agreement," said the World Resources Institute's Nirarta Samadhi, referring to a binding agreement on reducing emissions.

Norway -- which pledged in 2010 to pay Indonesia up to $1 billion if it preserved its rain forests -- committed $25 million to restore peatlands in the wake of the announcement.

The moratorium could also help prevent the outbreak of deadly smog from forest fires that shrouds the region every year, causing widespread illness.

Peatlands are moist and unlikely to ignite unless drained.

Hadi said the new regulation provided clearer guidance, ensuring no burning or draining was permitted.

Fires deliberately lit in 2015 across Indonesia's forests and peatlands were the worst in nearly two decades.

Research from Harvard and Columbia universities in the US estimate the crisis caused more than 100,000 premature deaths in Indonesia and neighbouring countries.

The World Bank put the economic impact at $16 billion -- twice Indonesia's clean-up bill in the wake of the devastating 2004 Indian Ocean earthquake and tsunami.