The extended Friday curfew, from 9am until 8pm, applies to the capital and the surrounding areas and is a response to protests called by an alliance of opposition parties.
A 25-hour curfew was imposed in Kathmandu on Thursday, which lasted until 3am on Friday.
With the protests and curfews crippling normal life in much of the capital, residents of Kathmandu rushed to the markets at dawn to get food and supplies before the curfew resumed on Friday.
State-run Radio Nepal said the curfew would also cover the suburbs of Lilitpur and Bhaktapur.
Another notice said a day curfew would also be imposed in Pokhara, a resort town 200km west of Kathmandu.
The notices warned people to stay indoors during the curfew hours and said those who violated the curfew order would be shot.
They said the curfews were imposed "to protect the people, property and peace."
But on Friday people had already begun to defy the 9am curfew.
In the western district of Kalanki, youths shouted "Down with the King" at
AFP reporters said burning tyres blocked roads on some city streets as well as on the outskirts beyond the curfew zone.
The alliance's "mass movement co-ordinating committee" pledged to step up the strike to force King Gyanendra to restore multi-party democracy in the Himalayan nation.
Clashes between security forces
and protesters continued on Friday
A statement said: "We appeal to all people to participate in the massive demonstration on Ring Road on Friday at 12 noon."
The strike "will continue with more intensity in the capital and across the country until further notice," the parties said.
Since clashes between security forces and tens of thousands of protesters began on April 6, 12 people have been killed.
The latest death was of a woman wounded during a protest in a district town on Wednesday, who later died in hospital.
King Gyanendra dismissed the government in February last year, saying it had failed to defeat Nepal's Maoist rebels, in which more than 13,000 people have died.
Gyanendra says Maoist rebels
have killed thousands of Nepalese
He has said he will hold elections by April 2007, but the parties say Gyanendra cannot be trusted and must hand over power to an all-party government immediately.
Local reports say the king is likely to name, Krishna Prasad Bhattarai, a former prime minister, to the post in an effort to appease the protesters.
But Bhattarai has apparently indicated he will only take the post if it is acceptable to the seven-party alliance.