Two anti-regime protesters died in Yemen on Sunday, a day after police shot them in the head, a medic said, raising the death toll to seven from demonstrations against President Ali Abdullah Saleh.
The two succumbed to wounds after "being shot in the head" in the southern city of Aden, said the medic, adding four other demonstrators were in a critical condition after also being shot in the head.
On Saturday, two other protesters were killed in Aden, one by police when they opened fire to disperse a demonstration and the other when demonstrators set fire to a police station in the city.
A medical official said Saturday hundreds of angry people had set ablaze the police station to protest the death of the protester earlier in the day. Several people were also wounded by gunfire, he said.
Elsewhere, a 12-year-old schoolboy was shot dead when police opened fire at a demonstration of students in the southeastern city of Mukalla.
And two other people died in the capital Sanaa on Saturday, one as police attacked demonstrators in University Square, where anti-government protesters have been staging a sit-in since February 21.
The other was shot dead by a sniper while walking to the square with a group of protesters.
Dozens of demonstrators were overcome by the tear gas, and friends used pieces of cardboard to fan them as they lay stretched out on the ground, many of them barely conscious.
Two doctors at the scene in Sanaa said that toxic gas, rather than
ordinary tear gas had been used against the protesters.
"The gas used by the police is strange. It causes cramps and a collapse of the nervous system," said Bashir al-Kahli, a doctor helping the injured.
The Interior Ministry denied using any sort of nerve gas and dismissed the claim as slander
The European Union, Britain and the United Nations condemned the brutal crackdown.
EU foreign affairs chief Catherine Ashton urged Saleh's government to honor promises he had made this week to protect demonstrators and uphold their right to free assembly.
The United States said it was dismayed by the growing fatalities and called for calm, warning that Yemen could suffer the same fate as Libya, where anti-government protests have spiraled into armed conflict between government and rebels.
Western countries and Yemen's neighbors increasingly fear that the growing chaos will make Yemen into a haven for al-Qaeda, which already uses it as a base, and a source of regional instability.
A series of political concessions by Saleh have failed to stem the tide of protesters frustrated with rampant corruption and soaring unemployment demanding his immediate resignation, and the police response has become tougher.
In Addis Ababa, Ethiopian Prime Minister Meles Zenawi bemoaned the fact that Yemen, also beset by rebellions in its north and south, had already become a base for the Islamist al-Shabaab rebels operating in Ethiopia's neighbor Somalia.
"If the demonstrations in Yemen lead to some sort of breakdown in law and order, this might give al-Qaeda ... a good opportunity to expand," he said.
As Yemen's water and oil resources dry up, it has become increasingly difficult for Saleh, 68, to fuel the patronage system that kept his tribal and political supporters loyal.