|The crackdown on protesters comes hours before the UN Security Council discusses the crisis in Yemen [EPA]
Security forces have opened fire on demonstrators in Sanaa and Taiz, south of the capital, killing at least three people and injuring hundreds.
The violence on Tuesday comes as the UN Security Council discusses the crisis in the country for the first time.
Pro-democracy protesters have been demanding for two months the resignation of Ali Abdullah Saleh, the president, who ruled the country since 1978.
The UN talks on the mounting turmoil in Yemen should be a strong signal to the country's president that bloodshed must avoided, Germany's UN envoy said.
"The fact that the council meets today on Yemen sends an important signal by the international community: the negotiations should not stall and further bloodshed has to be avoided," Germany's UN ambassador Peter Wittig said ahead of the talks.
Meanwhile, the UN children's fund said on Tuesday that 26 children have been killed during violent protests in Yemen over the last two months.
Marixie Mercado, a UNICEF spokeswoman, said that most of the children killed in clashes between security forces and anti-government demonstrators died of wounds from live ammunition.
"It is a sign of the growing attention that Yemen is attracting after Egypt, Tunisia and Libya," said a UN diplomat speaking on condition of anonymity, in reference to other protest-hit Arab states.
A Yemeni government delegation is expected to leave for Abu Dhabi on Tuesday for talks with the six-nation Gulf Co-operation Council (GCC) on its proposal for Saleh to transfer power to his deputy and end the crisis.
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Opposition representatives held similar talks on Sunday in Saudi Arabia.
Meanwhile, Yemeni lawmakers who split from the ruling General People's Congress party have established a new political group calling for Saleh's resignation, a statement from the bloc said.
The new group, named "Justice and Building Bloc", comprises former ministers and members of the parliament who had deserted the GPC in protest over the heavy-handed response by authorities to anti-Saleh demonstrations.
Members of the new group have called for "regime change" and the "immediate departure" of Saleh, according to the statement released late on Monday.
The bloc was announced in a ceremony on Monday in Sanaa, the capital.
It includes Nabil al-Faqih, former minister of tourism, Huda al-Baan, the minister of human rights, and Khaled al-Wazir, the transport minister.
Source: Al Jazeera and Agencies