British Prime Minister David Cameron begins a visit to Southeast Asia on Monday, looking to seal $1.2 billion in trade deals and push for greater cooperation in the fight against the Islamic State group.

Cameron will arrive in Indonesia on the first stop of a four-day trip, accompanied by 30 British business leaders and the trade minister, before heading to Singapore, Vietnam and Malaysia.

He will use meetings with President Joko Widodo of Indonesia and Prime Minister Najib Razak of Malaysia to discuss what he calls the "common enemy" of IS jihadists, who have seized vast swathes of territory in Iraq and Syria.

Hundreds of young Britons have joined IS in Syria and Iraq, sparking fears they could launch attacks on home soil upon their return. The threat from the jihadists is also in focus after IS claimed an attack on a Tunisian beach hotel last month that left 30 Britons dead.

Indonesia, which has the world's largest Muslim population and has long struggled with extremism, fears up to 500 of its citizens have been lured to the Middle East by IS, while nationals of Muslim-majority Malaysia have also joined the jihadists.

In remarks before the trip -- his first outside Europe since being re-elected in May -- Cameron said he would be talking to Southeast Asian leaders about "one of the biggest threats our world has faced".

"We will only defeat these brutal terrorists if we take action at home, overseas and online and if we unite with countries around the world against this common enemy," he said.

Britain would offer expertise on counter-terrorism, he added, and could also learn from Indonesia and Malaysia about what they have done to tackle extremism and build tolerant societies.

- 'Vast and dynamic market' -

With trade a major focus as Britain seeks to find new markets in fast-growing Asia, Cameron said that deals worth more than �750 million ($1.2 billion) would be struck during the trip.

"Over the next 20 years, 90 percent of global growth is expected to come from outside Europe and Britain must be poised to take advantage," he said.

"That's why I'm delighted to be taking British businesses to this vast and dynamic market, securing deals worth over �750 million and creating opportunities for hard-working people back at home."

Accompanying Cameron on the trip are senior figures from prominent British businesses including engine maker Rolls-Royce and construction equipment maker JCB.

He will also seek progress on a free trade deal between the European Union and the 10-member Association of Southeast Nations (ASEAN) during talks with the regional bloc's secretary general at its Jakarta headquarters.

In addition, Cameron will discuss action on climate change while in Indonesia ahead of a key summit in Paris later this year. Indonesia is one of the world's top greenhouse gas emitters, due in large part to rampant deforestation.

But there could be tension when Cameron meets Widodo Monday over the plight of a Briton on death row in Indonesia for drug smuggling.

Grandmother Lindsay Sandiford has said she fears her execution is imminent after a group of foreigners were put to death by firing squad in April, sparking international outrage.

The prime minister could run into controversy during his stop in Malaysia, with calls mounting for him to meet with the opposition as well as the government at a time Najib is fighting off a crisis.

The Malaysian leader is facing outrage over allegations that hundreds of millions of dollars were siphoned off from a state-owned development company he launched and retains close links with.

The premier and the company, 1Malaysia Development Berhad (1MDB), have both vehemently denied any wrongdoing. The case is being investigated by Malaysian authorities and a parliamentary committee.

Cameron will depart Jakarta on Tuesday for Singapore.

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