"There have been reports of imminent terrorist threats in Malaysia," Malaysia's police chief Khalid Abu Bakar said in a statement on Thursday night. "At this point, I would like to underline that they have yet to be confirmed."
Malaysia tightened security following terrorist attacks in France, Egypt and Lebanon, Khalid said.
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Security upped in KL for ASEAN summit
Obama is joining leaders of the 10-member Association of South East Asian Nations (ASEAN) for a weekend summit. Leaders from eight other countries with close partnerships with the grouping - Australia, China, India, Japan, New Zealand, Russia, South Korea and the United States - will also attend the meetings starting on Saturday.
At least 2,000 army personnel were being stationed at strategic points in Kuala Lumpur and another 2,500 were on standby, Armed Forces chief Zulkifeli Mohd Zin said.
Obama will meet Prime Minister Najib Razak on Friday and will "very directly" raise concerns about the status of Malaysia's political opposition, U.S. Deputy National Security Adviser Ben Rhodes said.
MUST READ: Obama to raise concerns on opposition in Malaysia - White House
"We are going to be very candid about areas where we have disagreements and differences and frankly objections if we see that the type of universal values that we support are not being respected," Rhodes told reporters on Thursday at the Asia-Pacific Economic Cooperation (APEC) summit in Manila.
Critics have accused Najib of escalating a crackdown on dissent and free expression after losing the popular vote in the 2013 general election.
MUST READ: Malaysia to continue pressing for people-centred ASEAN
The prime minister has come under pressure himself after it was revealed in July that nearly $700 million in unexplained deposits were placed into his personal bank accounts.
He has denied any wrongdoing but has yet to detail the source and purpose of the money he received.
Obama and most of the other leaders coming to Kuala Lumpur attended the APEC summit in Manila.
Obama has tried to turn the heat on China over its territorial claims in the disputed South China Sea and assure allies that a U.S. "pivot" to Asia remains a core policy.
MUST READ: China navy admiral says he is ready to respond to repeated breaches of Chinese sovereignty, in facing U.S. provocations in South China Sea
In talks with Philippine President Benigno Aquino, Obama demanded China halt land reclamation work that is turning seven reefs in the Spratly archipelago into islands.
Beijing has overlapping claims with Vietnam, the Philippines, Malaysia, Taiwan and Brunei in the South China Sea, through which $5 trillion in ship-borne trade passes every year.
China has said it does not want the South China Sea issue to be the focus of the meetings in Kuala Lumpur but acknowledged the topic would be hard to avoid.
The construction of airfields and other facilities on some of China's artificial islands has alarmed the region and raised concerns in Washington that China is extending its military reach deep into maritime Southeast Asia.
China's top admiral said his forces had shown "enormous restraint" in the face of U.S. provocations in the South China Sea, while warning they stand ready to respond to repeated breaches of Chinese sovereignty, according to a report on the defence ministry's website late on Thursday.
A U.S. warship tested the territorial limits around one of China's man-made islands last month, angering Beijing.