BY FRANCES ROBLES

Dozens of Cubans detained on their way to a Havana protest in defense of political prisoners were back home Friday, saying they are more determined than ever to keep up the pressure on behalf of their loved ones behind bars.

Authorities detained from two dozen people to about 40 on highways, homes and street corners in several provinces before dawn on Thursday. They were headed to a protest in front of the Ministry of Justice in Havana, activists on the island said.

When the sit-in took place at 1:30 p.m., most of the people who planned to picket were in detention. Only nine made it. Up to 40 would-be demonstrators picked up en route were detained all day and later released, some after more than 15 hours, according to the activists.

''For us this protest was very important,'' Laura Pollán, a member of the Ladies in White dissident group, said by telephone from Havana. Foreign Minister Felipe Pérez Roque ``was at the United Nations this week saying human rights are respected in Cuba and that there's freedom of expression. So we wanted to show that there is no freedom of expression and that you can't even protest the detention of your husband.''

Pollán's husband, Héctor Maseda, is an opposition journalist serving a 20-year prison sentence. He was one of 75 dissidents caught up in a 2003 sweep. About 60 are still being held.

Human rights activists say prison inmates complain of frequent beatings and several are not being treated for chronic medical conditions. Many of them are serving long sentences at facilities that are too far for their families to visit.

One political prisoner was transferred to an isolation cell at a prison far from his home after he denounced the killings of two inmates by prison guards, said Janisset Rivero-Gutiérrez, director of the Miami-based Democratic Directorate.

In an unusual show of coordination, dissident groups from throughout the island held rallies this week to protest the prison conditions. Several were held Monday, a religious holiday that honors the patron saint of prisoners.

A group of 38 members of Ladies in White -- female relatives of prisoners who stage Sunday protests dressed in white -- marched 2 ½ miles to a church, Pollán said, while in Santa Clara and Camagüey separate marches were held.

In Santa Clara, thousands gathered to watch protesters challenge conditions at the El Pre detention facility, dissident journalist Guillermo Fariñas reported.

Leading hard-line dissident Martha Beatriz Roque planned a sit-in Thursday at the Ministry of Justice, where she hoped to have a large group accompany her while she submitted a letter demanding the prisoners' release to Justice Minister María Esther Reus.

But it did not take much for the Cuban State Security apparatus to learn of the plans: dissidents signed petitions saying they would come.

At least 26 people who left their homes in Villa Clara 185 miles east of Havana were picked up before dawn, some of them on the National Highway, dissident journalist Guillermo Fariñas said.

Fariñas said he had planned to attend, but wound up spending the day outside the Villa Clara detention center, demanding his colleagues' release.

Only Roque, Pollán and seven others made it to the Justice Ministry, where dozens of pro-government hecklers surrounded them until government buses arrived to take the dissidents away. Pollán was dropped off at her house just a few minutes away in Central Havana.

''All of those released were let go with the warning that they could be charged at any moment with disturbing the peace,'' Fariñas told The Miami Herald by phone from his home in Villa Clara. ``If they are going to mistreat prisoners, we have to protest. Tomorrow that could be me, and I'd want people protesting for me.''

The press rights group Reporters Without Borders denounced the detentions, which included six journalists.

'Even though some of the arrested dissidents were immediately released, this crackdown is in part a reminder of the `black spring' of March 2003,'' the group said in a statement. ``Is the regime in Havana this time trying to rival that of [Myanmar], where a military clampdown has continued for several days and is holding the attention of the international community?''

U.S. Rep. Ileana Ros-Lehtinen of Miami sent a letter to European Union officials urging them to give the detentions as much as attention as the pro-democracy monks in Myanmar. Her letter said ``200 freedom-seeking individuals have essentially disappeared.''

But activists on the island say the number was closer to 40, and that all were accounted for.

The Cuban government did not make any statements about the roundup, and in general considers dissidents as ''mercenaries'' on the U.S. payroll.