At least seven people have been killed and dozens wounded after armed men loyal to President Ali Abdullah Saleh opened fire on demonstrators in the Yemeni capital, witnesses say.
Residents of Sanaa told Al Jazeera on Tuesday that several injured people were kidnapped after protesters calling on Saleh to step down were trapped by security forces inside the Al-Qaa neighbourhood.
According to the witnesses, armed men loyal to the embattled president had erected tents in the street to block an anti-government march.
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The protesters came under attack as they marched from Change Square to Al-Qaa, a district where government buildings are located.
It was the third time in four days that demonstrators had attempted to march from their base in Change Square on loyalist-held areas of the capital to be met by deadly gunfire.
Soldiers from the Republican Guard, a loyalist unit led by Saleh's son Ahmed, arrested four female protesters who were ahead of the main demonstration, activist Habib al-Uraiqi said.
Abdel-Rahman Berman of Yemen's National Organisation for Defending Rights and Freedoms (HOOD) said Saleh's forces used live ammunition and harsh tear gas.
Berman said HOOD team monitoring the situation charged that government forces and thugs abducted female protesters and some wounded demonstrators in a "shameful and criminal way".
Similar demonstrations were held in other parts of Yemen, including the southern cities of Aden and Taiz, protest organisers said.
The latest violence came as the United Nations condemned the killing of peaceful protesters in Yemen.
"We condemn in the strongest terms the reported killing of a number of largely peaceful protestors in Sanaa and Taez as a result of the indiscriminate use of force by Yemeni security forces since Saturday," Rupert Colville, a spokesman for the UN High Commissioner for Human Rights, said.
"We are extremely concerned that security forces continue to use excessive force in a climate of complete impunity for crimes resulting in heavy loss of life and injury, despite repeated pledges by the government to the contrary," he added.
On Tuesday, key members of the Security Council began considering a British-drafted resolution that would call for an immediate cease-fire in Yemen and transfer of power, as well as immediate action by Yemeni authorities to end attacks against civilians.
The consultations are still in progress.
Tawakkul Karman, Yemen's Nobel Peace Prize laureate, on Monday urged the UN to act "immediately and decisively" to halt a deadly government crackdown on protesters.
In a letter to Ban Ki-moon, the UN secretary-general, she said: "This is the only thing that will give Yemenis... confidence that international justice exists... and that it extends far enough to reach Saleh, his gang and all the despots who continue to kill innocents."
Karman and tens of thousands of other pro-democracy activists have for months been camped out in Sanaa's Change Square, demanding an end to Saleh's long rule.
The crackdown by government troops on anti-government protests has killed hundreds since the mass protest movement, inspired by uprisings in other countries in the region, began in late January.