Opposition parties in Nepal say police have detained dozens of their leaders and workers on the first day of their four-day general strike.
Nepalese authorities have banned political rallies in Kathmandu
The opposition is protesting against King Gyanendra's seizure of power more than a year ago.
Correspondents say the general strike has affected normal life and most shops and offices are closed.
Meanwhile, 10 people, including five policemen and three rebels died in a clash in the south, officials say.
More than 13,000 people have been killed in violence since Maoist rebels took up arms 10 years ago.
The latest protest has been organised the Nepal's seven-party opposition alliance.
A prominent student leader, Gagan Thapa, told the BBC that at least 55 opposition workers had been detained.
A partial night curfew was imposed in parts of Kathmandu from 2300 local time on Wednesday until 0300 on Thursday. The curfew was necessary for "security reasons," officials said.
Security was tight in the city and most roads were deserted on Thursday morning, reports said.
"The streets are empty. There are no vehicles. I walked for half an hour to get to work," hotel worker Manisha Shahi told the Associated Press news agency.
"But it is not safe to walk.... Anything could happen."
A mass anti-monarchy rally is planned for Saturday despite a ban on public protests in Kathmandu.
Nepalese authorities cracked down on demonstrators on Wednesday, arresting more than 100 people.
The strike is the latest in a series of protests over King Gyanendra's seizure of executive powers in February last year.
A new ban on political rallies in some areas of Kathmandu came into force on Wednesday. The authorities say they fear Maoist rebels plan to incite violence.
The United Nations and the US have criticised the ban on rallies and the arrest of opposition leaders and workers.
The opposition recently formed a loose alliance with the rebels to step up the pressure on the king to end his direct rule.
The Maoist rebels say they have suspended activities in Kathmandu but the government says they have infiltrated opposition rallies.
In the latest fighting, five policemen, three rebels and two civilians were killed in clashes in Malangwa, in the southern district of Sarlahi, local officials say.
District authorities said rebels attacked a number of government offices and set them on fire.
A number of government officials, including the chief district officer, Bodh Raj Adhikari, have been reported missing after the clashes.
An army helicopter carrying 10 security personnel which was sent to the area had crash-landed, security sources told the BBC.
It is not clear whether there were any casualties after the incident.
The rebels say they shot down the helicopter.
Are you affected by, or taking part in, the strike? Send us your comments using the form below.
In Thamel, the usually busy tourist centre, most shops are closed with a few more opening this afternoon. There are no cars in the streets and even though there is calm in Thamel people are definitely more alert than usual.
Louisa Greenwood, from London, UK but currently in Kathmandu
I am staying as a visitor in Kathmandu and witnessed the first day of the general strike. Almost all shops are closed (except some pharmacies and very few shops catering for tourists in the Tamel area of Kathmandu). However, street vendors have not missed the opportunity to sell their goods without competition by shops. Truckloads of riot police (including female agents) can be seen at strategic points such as Hanuman Doka (old royal palace), New Road and Ason Tole in the Old town. I would consider walking around not as dangerous for tourists. For the tourist the strike presents an opportunity to walk around Kathmandu and neighbouring Patan unmolested by vehicular traffic and pollution.
Bertsch Wolfgang, Germany
I had to walk for almost two hours to reach the office. Coming back home was the same ordeal. The businesses, offices, schools etc were all closed down and major streets wore a deserted look. However, ordinary Nepali neither support the political parties and their demonstration nor the repressive action from the king's part. Both of them have been thoroughly tested over the time and do not own support from ordinary people. The same is the case with the Maoists. The need of the hour is peace and all of them have failed to respond.
Prajjwal Rana, Kathmandu, Nepal
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