Hundreds of Maoist cadres and leaders held rallies in here commemorating the so-called 'People's War', the decade-long insurgency that began in 1996, killing over 16,000 people.
The civil war ended in 2006 as the Maoists laid down arms and joined the peace process.
Two years later in 2008, the Hindu monarchy was abolished as the country was declared a republic and a secular state as the Maoists came to power winning the general election with Prachanda becoming prime minister. But they were ousted in the next constituent assembly polls in 2013.
Addressing a programme on the occasion, former premier Prachanda urged the people to move forward with the country's new constitution by institutionalising the achievements of past movements.
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"The constitution is the product of our war and we take ownership of the new constitution," he said highlighting the role of his party in ushering in republicanism, federalism, secularism, and inclusive representation spurred by the people's war and formation of the Constituent Assembly.
But the new charter has triggered political chaos in the country with the Madhesi community, largely of Indian-origin, leading six-month-long violent protests demanding better political representation, redrawing of provincial boundaries and the federal structure of the Constitution.
The violence killed 55 people before being called off this month even as both sides failed to break the deadlock.