Madhav Baskota, the general secretary of the Nepal Bar Association, said two lawyers were hit with rubber bullets and one with a tear gas canister fired by police, who also used batons to beat them on Thursday.
The United States cancelled a congressional visit to Nepal and allowed some embassy workers to leave the Himalayan nation after a fourth fatal shooting by security forces during increasingly violent pro-democracy demonstrations.
Dozens of lawyers were wounded after police hit them with batons while at least 70 were arrested, Baskota said.
The demonstration began when about 500 lawyers came out of the association's office in the heart of Kathmandu waving banners and shouting anti-government slogans in a campaign to get King Gyanendra to relinquish direct control over the government.
The association office is next to a compound containing all of the government ministries and across from the army headquarters.
The government has banned rallies in Kathmandu and surrounding areas, and hundreds of people defying the ban have been beaten and arrested by the police since last week, when the country's alliance of seven main political parties called a general strike to demand that the king should restore democracy.
Lawyers shout anti-royal slogans
during a protest in Kathmandu
The protesting lawyers managed to march a few metres when they were stopped by police who beat them with bamboo batons, fired a few rounds of tear gas and opened fire.
A general strike continued on Thursday, closing schools and businesses.
While some shops opened in Kathmandu so people could buy supplies, highways were deserted and trucks bringing food and fuel to cities were stranded in southern Nepal, according to the highway patrol. Not a single bus had arrived or left the bus station in Kathmandu for more than a week, said a guard at the station.
The strike was initially called for four days last week, but the opposition parties decided to extend it indefinitely, with the backing of the country's communist rebels.
More protests were expected in parts of Kathmandu and elsewhere in Nepal, officials and opposition leaders said.
"The country is day by day going bad. If I demonstrate and then there is peace, then we can have business," said Chandra Pokhrel, a 31-year-old trekking guide who was getting ready to take part in a protest on Thursday.
Kathmandu residents buy produce
after a curfew was lifted Wednesday
The strike and protests prompted the US Embassy in Kathmandu to start allowing family members of staff and non-emergency American employees to leave. The embassy's consular office and a library were closed.
"Due to ongoing violence, curfews, and widespread insecurity in Nepal, the US mission is reducing its activities," the US state department said on its website.