Scuffles have broken out between riot police and protesters calling for Nepalese Prime Minister Baburam Bhattarai to resign, in the ancient Nepali city of Bhaktapur.
The opposition protesters were attempting to block the prime minister and other Unified Communist Party of Nepal (UCPN) Maoist leaders from getting to the party's annual conference on Saturday.
Police used batons in an attempt to disperse the crowd, who shouted anti-government slogans at vehicles with Maoist party supporters onboard.
Local media reported that at least five protesters had been injured during the demonstration.
The clash on Saturday comes after activists from several opposition parties hurled stones at rivals and erected barricades outside the venue of a Maoist conference in the provincial town of Dailekh on Wednesday.
The demonstrations are raising tensions that threaten a peace process in a country still recovering from a decade of civil war.
It is the first time the Maoists and opposition parties have clashed since parliament was dissolved in May, having failed to finalise a new constitution seen as key to the country's long-term stability.
Pressure on Prime Minister Bhattarai, 58, is mounting after he failed to hold the elections he ordered for November last year.
Despite the opposition activists' efforts, the prime minister managed to reach the party conference and assured the crowd an election would be held soon.
"I want to assure you from the side of the government, that a way out will be made very soon to hold the election. I ask you all to be assured of that," said Bhattarai.
The opposition parties want Bhattarai to quit to pave the way for the formation of a national unity government to oversee parliamentary elections expected in May.
The leader of the main opposition party, Nepali Congress (NC), spoke to crowds at another demonstration on Friday.
"I don't think it is proper for us to pay taxes just to fill in the pockets of the prime minister," said NC leader Manmohan Bhattarai.
The Maoists waged an armed struggle against the country's now toppled monarchy. They joined the political mainstream in 2006 after the end of the civil war that killed more than 16,000 people.
They won elections two years later and are now leading a coalition government in the impoverished Himalayan republic.