Several shark species and the manta ray won international trade protection Monday in a move hailed by conservationists as a breakthrough in efforts to save them from being wiped out by overfishing.

The deal at a major wildlife conference in Bangkok marked a rare victory in the fight by environmentalists to reverse a slump in populations of sharks -- the world's oldest predator -- due to rampant demand for its fins.

Rather than a complete ban, the 178-member Convention on International Trade in Endangered Species (CITES) voted to restrict cross-border trade in the oceanic whitetip, the porbeagle, three types of hammerheads and the manta ray.

The agreement, which must still be formally approved by the CITES plenary session, delighted conservationists who warn that Asia's voracious appetite for shark fins is causing their population to plunge.

"The tide is now turning for shark conservation," said Elizabeth Wilson of Pew's Global Shark Conservation Campaign.

"With these new protections, oceanic whitetip, porbeagle, and hammerhead sharks will have the chance to recover and once again fulfil their role as top predators in the marine ecosystem."

Monday's deal would require countries to regulate trade by issuing export permits to ensure their sustainability in the wild, otherwise they could face sanctions by members of CITES, a global treaty which protects some 35,000 species.

Under the CITES framework, however, a party may ask to reconsider the decision at the plenary session, as happened in 2010 when an initial agreement to control international trade in the porbeagle was later overturned.

Conservationists say sharks are slow to reproduce and may become threatened with extinction without better monitoring and management.

"During their lifetimes they have relatively few offspring and they only start reproducing at a relatively late age -- they're more like mammals in many ways than fish," said Colman O'Criodain, an expert with the WWF.

Asian nations led by Japan and China -- where shark fin soup is considered a delicacy -- tried in vain to block the proposals, which were pushed by countries including Brazil, Colombia and the United States.

If the deal gets final approval, the five species would join the great white shark, the whale shark and the basking shark, which already enjoy international trade controls. Members would have 18 months to introduce the new measures.

Humans kill about 100 million sharks each year, mostly for their fins, according to the UN Food and Agriculture Organisation (FAO), and conservationists are warning that dozens of species are under threat.

Ninety percent of the world's sharks have disappeared over the past 100 years, mostly because of overfishing in countries such as Indonesia, the FAO says.

Conservationists also argue that "finning" -- slicing the valuable fins from live sharks -- is inhumane, as the rest of the animal is typically dumped back into the ocean where it bleeds slowly to death.

Shark fin soup was once a luxury for China's elite, but shark populations have been decimated around the world as the country's 1.3 billion people have grown wealthier and incorporated it into their festivities.

"The trade is driven by the demands of a luxury market, whether it's shark fin soup for banquets in China, porbeagle meat in Europe where it's considered a delicacy or the gill plates in the manta ray which are used in Chinese medicine," said the WWF's O'Criodain.

Hong Kong is the world's largest shark fin market with about 50 percent of the global trade, according to campaign group Pew.

The CITES meeting is also discussing how to tackle illegal trade in ivory and rhino horn with environmentalists calling for wildlife trade sanctions against countries which fail to take sufficient action.

A proposed ban on international trade in polar bears was rejected last week, with opponents warning that it would distract from the bigger threat from global warming.