MANAGUA, NICARAGUA, AUG. 15 -- Sandinista police arrested the head of Nicaragua's nongovernmental human rights commission and a number of opposition demonstrators today after breaking up an attempt to hold a protest march.

Witnesses said Lino Hernandez, the head of Nicaragua's Permanent Commission on Human Rights, was seized after 200 anti-Sandinista demonstrators gathered in a street outside the new headquarters of the Democratic Coordinating Council, an opposition umbrella group. The witnesses said Hernandez, who is not a member of that group, had been invited to the inaugural ceremony and was watching the demonstration when he was arrested.

According to Carlos Huembes, the president of the coordinating council, police struck Hernandez while they were arresting him. Also detained, Huembes said, were Alberto Saborillo, a leader of the Nicaraguan Conservative Party, and an undetermined number of others.

An administrator of the human rights commission, Luz Marina, said Hernandez and Saborillo were being held on charges of "disturbing public order."

The human rights commission documents alleged abuses by the Sandinistas, while a governmental commission and other groups focus on alleged violations by the Nicaraguan rebels, known as contras.

Witnesses said today's disturbance started when council members left the new headquarters and tried to hold a demonstration to test the political climate under the regional peace agreement signed last week by Nicaragua and four other Central American states. Sandinista police, with dogs, surrounded the area and told the protesters they needed a permit. Scuffling began when pro-Sandinista groups called "turbas" arrived to try to break up the protest, the witnesses said.