Tens of thousands of people attended the event organised by Hun Sen's ruling Cambodia People's Party (CPP), which has dominated the country since it was installed by the Vietnamese forces which toppled Khmer Rouge leader Pol Pot on January 7, 1979.
The gathering -- which had a much larger turnout than in previous years -- comes as Hun Sen's control over Cambodia is firmer than ever following the systematic removal of his rivals before a July election.
Speaking before a sea of supporters today, Hun Sen took credit for the stability and growth his government has overseen since the Khmer Rouge era. At least 1.7 million Cambodians died during the regime's fanatical Maoist rule from 1975-79.
Most died through execution, starvation or overwork during the group's attempts to transform the country into an agrarian utopia.
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Hun Sen, a former Khmer Rouge cadre who later defected and joined the resistance, frequently reminds the public of Cambodia's horrific past and warns that fresh unrest could break out if his government is ousted.
Rights groups strongly disagree, saying the move plunged Cambodia's fragile democracy into peril.
The US and EU have withdrawn support for the July election due to the ruling, saying the vote would not be legitimate without the now dissolved Cambodia National Rescue Party (CNRP), which enjoyed significant public support.
Hun Sen has responded by ramping up his ultra-nationalist rhetoric, reiterating today that "Cambodia does not bow to external pressure".
But while the premier boasts about the stability and economic growth nurtured during his time in office, critics point out the myriad rights abuses and endemic corruption that have flourished under his watch.
Some Cambodians have also criticised the celebration of the January 7 anniversary, saying it represents the start of a decade-long occupation by Vietnam rather than a day of liberation.