Riot police armed with rifles arrested at least 150 people Sunday to prevent marches by pro-democracy demonstrators demanding the government lift its 29-year-old ban on political parties. The protesters, shouting ``Long live the revolution!'' were taken into custody as they entered Katmandu's main shopping district of New Road to begin marching, said witnesses who spoke on condition of anonymity. The planned march was one of several scheduled around Nepal by two banned political groups, the Nepali Congress Party and a left-wing coalition, who are leading a movement for more political freedom. Political demonstrations are not allowed in Nepal. According to the government, at least 12 people have been killed since Feb. 18 when the movement was launched to demand restoration of a multiparty democracy. Activists say the death toll is nearly double the government figure. Activists said at least 1,000 people were taken into custody Sunday, mostly in the capital, but the witnesses, who have proved reliable in the past, said they only saw about 150 people being herded into a police station. The police refused to give any figures. Residents contacted by telephone said police also arrested demonstrators in the southeastern town of Dharan on Sunday, but they had no details. The outcome of the other planned marches was not immediately known. The state-run news agency said without elaborating that ``some persons who tried to raise undesirable slogans'' were arrested in the southern town of Nepalganj. The report was the only reference by the government to any demonstration in the Himalayan kingdom, one of the world's oldest monarchies. Witnesses said those arrested in Katmandu included Hari Bol Bhattarai, former mayor of the city and a senior member of the Nepali Congress, and Padma Ratna Tuladhar, a left-wing member of the National Assembly. Both were waving the black flags adopted by the new pro-democracy movement and were shouting anti-government slogans when policemen tore the flags from their hands and took them away, said witnesses. Earlier Sunday, more than 100 doctors and nurses in the country's largest hospital walked off their jobs for more than one hour in support of the pro-democracy movement. They gathered outside the 300-bed Bir Hospital in the capital, wearing black armbands over their white jackets. ``We mourn the death of our people,'' said one doctor, who refused to give his name for fear of reprisals. ``This is a protest against the government's violation of human rights.'' Medical students said in a statement they supported the movement. In Katmandu, hundreds of steel-helmeted policemen, wearing chest pads and carrying rifles, batons, bamboo shields and tear-gas canisters, patrolled the 2-square-mile New Road area, watched by reporters and throngs of tourists. Shops were closed, and only police vans and a few private vehicles were allowed in the usually bustling area. The government has accused the demonstrators of trying to impose their brand of democracy on a country which it says already has a working democracy. Power in Nepal is shared between the king and the National Assembly. One-fifth of the assembly's 140 members are nominated by the king. The rest are elected on a non-party basis. Advocates of multiparty democracy say the elections are a farce and that the only candidates allowed are those approved by King Birendra or his associates. Nepal's two-year experiment with Western-style democracy ended in 1961 when then-King Mahendra, the present monarch's father, dissolved the government of the Nepali Congress Party, accusing it of corruption and poor administration.