"Activists of five pro-parliamentary parties were arrested in four places in the country Sunday afternoon for holding anti-king protests," a Nepali Congress party source said on Sunday.
The demonstrators distributed leaflets in the streets and shouted slogans against the king while demanding reinstatement of multi-party democracy and the return of fundamental rights, witnesses said.
Nepal's King Gyanendra sacked the government and declared a state of emergency in a move that has drawn international condemnation.
Dozens of arrests have been made during earlier rallies, which have been banned as part of the security measures put in place since the king came to power.
Crackdown on press
Authorities were unavailable to confirm the arrests made on Sunday.
Gyanendra's transition from constitutional to absolute monarch has also seen a crackdown on press freedoms, and two Nepalese journalists were arrested on Sunday while participating in a programme held by a journalists' association.
So far, nine journalists have been detained by the government after the king's moves on the government, which he accused of failing to hold elections or control the Maoist rebels.
Gyanendra said he had to take such steps to control the ongoing insurgency which has claimed more than 11,000 lives since it was launched in 1996.