Shops and businesses shut across much of the country on Saturday as the opposition pressed a general strike. Tensions had eased in the previous two days due to the Nepali New Year holiday.
About 200 journalists tried to march through Kathmandu on Saturday morning to demand increased press freedom and the release of dozens of reporters detained since King Gyanendra seized absolute power 14 months ago.
Police blocked the rally and charged with batons, injuring seven people and detaining at least a dozen, organisers said.
Calls for democracy
Later, thousands of people marched for miles along the ring road encircling the capital, shouting: "Down with the monarchy! Salute the republic!"
Subash Nemwang of the Communist Party of Nepal, one of the seven opposition parties organising the strike and protests, said: "Life will be brought to a standstill."
A Kathmandu marcher, 24-year-old agriculture student Ujwal Dhakal, said: "There should be no constitutional monarchy. There should be pure democracy because the monarchy has been very bad to the people of Nepal."
The protest remained peaceful until demonstrators tried to enter the city centre, where rallies are banned.
"There should be no constitutional monarchy. There should be pure democracy because the monarchy has been very bad to the people of Nepal"
Demonstrator Ujwal Dhakal
When police blocked their way across a small bridge, a brief melee broke out as officers beat them back with batons and fired a few cylinders of tear gas.
No one was injured in the skirmish, which ended within minutes. The protest ended a short while later.
There were demonstrations in numerous other towns and cities demanding that Gyanendra relinquish power, officials and local media reported.
Gyanendra said he took control of the government to restore political order and end a communist insurgency that has left nearly 13,000 people dead in the past decade.
The protests, which began April 6, are the worst unrest Gyanendra has faced since seizing power.
Four people have been fatally shot and hundreds have been beaten, fuelling anti-royal sentiment and prompting criticism from the United Nations.
The seven main opposition parties decided late on Friday to continue with the strike and protests after Gyanendra offered few concessions in his annual New Year's message.