A grinning Prime Minister Hun Sen walked up to US President Barack Obama and shook his hand in California yesterday, lending the premier his long-sought aura of legitimacy even as hundreds of angry Cambodians protested his 31-year rule less than half of a kilometre away.

The ASEAN summit that kicked off yesterday at the Sunnylands resort in Rancho Mirage is the first ASEAN meet held in the United States, and all but two of the leaders of the 10-nation bloc are in attendance.

While the meet has been criticised by human rights groups for legitimising Southeast Asian “strongmen” like Hun Sen and the communist rulers of Vietnam and Laos, it was hailed by President Obama as a sign of the US’s closer ties with the region as the superpower continues its pivot to Asia.

In remarks to reporters, Obama indicated the two-day summit would address trade and the South China Sea dispute, an issue Cambodia was accused of stonewalling due to its strong China ties during 2012’s ASEAN summit.

Hun Sen, who had offered pointed critiques of US policy during a meeting with CPP loyalists after arriving, kept his remarks vague during the summit’s first session, praising the warming ties between ASEAN and its host, according to state news outlet AKP.

The high-level meeting, which will last through Tuesday in the US, also saw the presence of hundreds of protesters from Southeast Asia and anti-globalisation groups on a street corner several hundred metres from the Sunnylands complex.

The protest was closely watched in Cambodia after similar protests during Hun Sen’s visit to Paris in October resulted in a counter-protest the next day in which members of a pro-ruling party mob savagely beat two opposition Cambodia National Rescue Party lawmakers.

Cambodian-Americans were one of the larger contingents during yesterday’s protest, waving placards demanding a “corrupt” Hun Sen step down from power, and calling him a “murderer”, “tyrant” and “traitor.”

The protest was peaceful and lasted from 8am to about 3pm in searing 32-degree heat, according to Cambodia-America Alliance vice president Touch Vibol. “Hun Sen’s 35 years in power is marked with corruption, human rights violations, illegal land violations and a corrupt courts system,” he said.

Despite publicly suggesting he would shake the protesters’ hands on Monday, Hun Sen did nothing of the sort, and protesters were unable to identify which of the tinted cars contained the Cambodian delegation as they drove to Sunnylands.

“But I can tell you then when any vehicle passed by, we made some noise,” Vibol said, maintaining that 1,500 people attended the protest.

Brett Kelman, a reporter for the local Desert Sun newspaper who was at the scene, estimated the protesters numbered about 600 at their peak.

In the wake of the beatings in October, protest organisers and the CNRP have repeatedly distanced themselves from each other. As of yesterday, it remains unclear whether any retaliation might still take place, however.

The authorities, who had previously pledged to provide security, could not be reached yesterday. Neither could Saing Sun, head of the Will of Overseas Youth, a CPP-aligned youth group that vowed counter-protests last week, nor high-ranking CNRP officials.

Government spokesman Phay Siphan yesterday dismissed the protesters as “living in the past of the Cold War”, because Cambodia was a “democracy” now. But there would be no reprisals, he said, explaining that Interior Minister Sar Kheng would ensure the protection of concerned opposition lawmakers.

Sebastian Strangio, author of Hun Sen’s Cambodia, said that while there had been “ominous noises”, whether or not reprisals might still take place remained anyone’s guess, especially after the recent public expressions of concern by the US and its embassy.

Despite calls for Obama to focus on human rights during the meeting from a group of seven US senators and 34 members of congress, Strangio said the US’s references to the topic would be largely “ceremonial and ornamental”.

“[The US] is trying to compete with a country, China, that doesn’t care a whit about human rights [in Southeast Asia],” he said.

Additional reporting by Alessandro Marazzi Sassoon and Meas Sokchea