BEIRUT (AP) — A young woman was found beheaded and mutilated, apparently by Syrian security agents, underscoring what witnesses and the U.N. human rights office said Friday was a fearsome new tactic of retaliating against protesters' families to snuff out the 6-month-old uprising against the regime of President Bashar Assad.

The slain 18-year-old, Zainab al-Hosni, is believed to be the first woman to die in Syrian custody since the uprising began in mid-March. Amnesty International said Friday she had reportedly been detained by security agents to pressure her activist brother to turn himself in.

The violence serves as a grim reminder of how the Assad family has kept an iron grip on power in Syria for more than 40 years by brutally crushing every sign of dissent. The idea that the regime has eyes and ears everywhere resonates in a nation of 22 million where decades of autocratic rule have nurtured a culture of deep fear and paranoia.

Witnesses and activists say retaliation against families of those involved in the uprising has ranged from threatening phone calls to beatings and even killings, as in the case of al-Hosni.

The U.N. human rights office said Friday that the harassment was even extending beyond Syria's borders.
"Prominent human rights defenders, inside and outside the country, are reported to have been targeted," U.N. human rights office spokeswoman Ravina Shamdasani said in Geneva. "We are also concerned by reports of the targeting and attacking of families and sympathizers of the protesters by security forces."

She offered no details and did not elaborate on the activists or their families being targeted outside the country.
The Syrian opposition movement has proved remarkably resilient despite a massive military assault using tanks, snipers and shadowy, pro-regime gunmen against demonstrators. According to U.N. estimates, more than 2,700 civilians have been killed in the crackdown since March and thousands more have been detained since protests began in mid-March, riding on the wave of euphoria as popular uprisings toppled longtime dictators in Egypt and Tunisia.

The mutilated teenager, al-Hosni, was from the central city of Homs, one of the hotbeds of the uprising. She was seized by men in plainclothes on July 27, apparently to pressure her brother Mohammed, who was organizing protests in the city, Amnesty said.

After her arrest, he was told by telephone that she would only be released if he stopped his activities, the New York-based group said. Her brother was eventually arrested earlier this month. On Sept. 13, his mother was summoned by security forces to pick up his body, which showed bruises, burns and gunshots, the group said.
At the same morgue, the mother happened to find her daughter's body as well. The family said Zainab had been decapitated, her arms cut off, and skin removed, according to Amnesty.

After Zainab's burial last weekend, women held a protest in Homs, hailing her as the "flower of Syria" and chanting "Syria wants freedom" and "The people want the president's ouster," according to video footage posted on the Internet by local activists.
"They plucked the flower, and she said, 'After me, a bud will rise up.' Rejoice in eternal paradise, Zainab," read a sign held by one of the women.

The deaths of Zainab and her brother bring to 103 the number of people who have been reported killed in Syrian custody since the uprising began in March, Amnesty said.
"If it is confirmed that Zainab was in custody when she died, this would be one of the most disturbing cases of a death in detention we have seen so far," said Philip Luther, Amnesty's deputy director for the Middle East and North Africa.

The Syrian government has banned foreign journalists and placed heavy restrictions on local coverage, making it difficult to independently verify events on the ground.
But there have been growing reports in recent months of activists' families facing bloody retribution, including parents of Syrian pianist Malek Jandali.

In July, Jandali participated in a rally in Washington, pressing for freedom in Syria and performing a piece he wrote called "I Am My Homeland." Soon after, he said, pro-government gunmen stormed his parents' house in Homs and beat his father, Maamoun, and his mother, Lina.

Jandali posted photographs of his parents' bloodied faces on his Facebook page this week.
Still, the uprising has continued. Friday protests have become a weekly ritual in Syria, despite the near-certainty that security forces will respond with bullets and tear gas.

This Friday, Syrian security forces opened fire on thousands of protesters calling for the opposition to unite against Assad's regime. The Syrian opposition is fragmented and has not yet formed a united front that would offer an alternative to Assad.

Several people were killed Friday in Damascus and near Homs, although there was no clear figure — a common problem in the confusion of widespread protests. One activist group, the London-based Syrian Observatory for Human Rights, put the death toll at nine.

An activist in Homs, Majd Amer, said there was unprecedented security presence in the city.
"They have been deploying here since last night," said Amer as cracks of gunfire could be heard in the background.
Also Friday, the European Union agreed to widen sanctions against Syria by banning investment in the country's oil sector. EU foreign affairs chief Catherine Ashton said that the new measure seeks to reinforce the ban on Syrian crude oil imports agreed on Sep. 2.

Friday's additional measures also include a ban to deliver bank notes to the Syrian Central Bak and travel and visa bans on more officials linked to the regime.
Syria exports some 150,000 barrels of oil per day, with the vast majority going to the European Union. The EU says that Syria earned euro3.1 billion ($4.4 billion) by selling oil to the EU in 2010.

With the new investment ban, the EU seeks to target Syrian companies that explore and refine crude oil. It says that EU based operators can no longer participate or set up joint ventures with such Syrian companies, and are no longer allowed to provide credits and loans.
"Repression against the Syrian people must stop completely," Ashton said.
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AP writer Frank Jordans in Geneva contributed to this report.