Security forces in Syria on Wednesday arrested more than two dozen protesters in the capital Damascus, in a second day of rare protests that are banned under emergency laws in place since 1963.
Despite the ban, some 200 people took to the streets of Old Damascus on Tuesday, calling for liberty and political freedoms and on Wednesday dozens of relatives of political prisoners demonstrated to demand their release.
"Free the prisoners!" the protesters chanted as they gathered in Marjeh Square near the interior ministry in central Damascus where they were joined by several human rights activists, AFP correspondents and witnesses said.
Large numbers of police and security agents in civilian clothes ringed the protesters and four young demonstrators were arrested and whisked away by car, the sources said. No violence was reported.
But the Syrian Observatory for Human Rights (SOHR) said "more than 25 people" were arrested, including Kurdish blogger Kamal Hussein Sheikho.
Sheikho was released from prison on bail of 500 Syrian pounds ($10) on Sunday, although he is still on trial for allegedly publishing material harmful to the country.
Author Tayeb Tizini, rights activists Mazen Darweesh, Nahed Badawiya and Suhair Atassi were also detained, along with five relatives of prominent opposition figure Kamal Labwani who is serving a 12-year jail term, including his son Omar, the SOHR said.
On Tuesday Atassi paid tribute to "the Syrian people who took the initiative ahead of the opposition," recalling the popular uprisings that shook Tunisia and Egypt.
"It's the first time a demonstration calling for freedom has taken place in Syria," she told Al-Jazeera television, expressing her "surprise."
A Facebook page entitled "The Syrian revolution against Bashar al-Assad 2011," which has amassed about 42,000 fans, had been promoting demonstrations "in all Syrian cities" on March 15.
Dozens of Syrians responded to the call and marched on Tuesday in the landmark Al-Hamidiyeh souk and nearby Hariqa souk of Old Damascus, chanting: "God, Syria, liberty" and "Syrians, where are you?"
The families of 21 jailed human rights activists announced in an online statement on Saturday their plans to lobby Interior Minister Saeed Sammur for the release of their relatives.
"We have decided to give the interior minister next Wednesday at noon a letter outlining our complaints and suffering," they said a statement posted on the SOHR website.
"After a long wait and rumors of an impending release of prisoners of conscience in Syria, our hopes have vanished."
The detainees, some of whom have spent several years behind bars, include human rights lawyers Anwar Bunni and Muhannad al-Hassani, as well as engineers, doctors and writers.
The protesters were unable to deliver the letter, said the head of the Syrian League for the Defence of Human Rights Abdel Karim Rihawi. Officials told them they must first submit a request to see the minister, he added.
An interior ministry official told reporters: "It is natural to receive the relatives at the interior ministry and to listen to their complaints."
But he accused "some people who exploited this occasion and infiltrated among the ranks of these families to launch some slogans."
Meanwhile, dozens of supporters of President Bashar al-Assad staged a counter-demonstration in Marjeh Square, waving Syrian flags and chanting slogans in his support, AFP correspondents said.
Syrian human rights groups denounced Wednesday's arrests, saying the authorities "reacted with exaggeration" to peaceful demonstrators.
"It is a violation of the right to assemble, which is stated in the Syrian constitution," Rihawi told AFP.
The SOHR issued a statement urging the authorities "to immediately release all those arrested" and to "stop arbitrary arrests" of regime opponents.
It also demanded "a modern law to organise the work of political parties and civil associations."
On Tuesday Foreign Minister Walid Muallem said political reforms would be implemented this year.