Yemeni forces opened fire on demonstrators in three cities on Wednesday, killing at least nine and wounding scores in escalating bloodshed that could ramp up public fury at the president's refusal to step down.
In the capital Sanaa, forces fired on a crowd of tens of thousands marching to the cabinet building. At least six demonstrators died and around 100 were wounded, said a doctor heading a makeshift clinic for wounded protesters at the scene.
He said the number of dead could rise.
In the industrial center Taiz, snipers killed two protesters and dozens were injured by gunfire, tear gas and bat-wielding plainclothes security men. Protesters retaliated by torching a police building and sealing off government buildings.
In the Red Sea port city of Hudaida, one protester was killed when security forces opened fire after marchers tried to force their way into a government building, witnesses said.
The bloodshed will fuel public rage ahead of Friday, traditionally the main day of unrest during a three-month-old revolt against President Ali Abdullah Saleh inspired by uprisings across the Arab world.
'Massacre'
Crowds have lost patience with stalled negotiations to end Saleh's 33-year rule, and violence is surging in a country where half the population owns a gun.
"This is a massacre, they are opening fire randomly," Mohammed al-Qibly, a leader of a youth protest movement in Sanaa, told Al Jazeera television. "The scene is terrifying in every sense of the word."
Witnesses in the capital said some 40 people were shot and protesters stopped to help treat the wounded, who were rushed away in private vehicles as the gunfire crackled.
"Forces opened fire heavily when protesters got around 200 meters away from the cabinet, but the protesters didn't back away at first," Yemeni journalist Abdulsattar Mohammed said. "A number of injured fell and they were carried away to hospital on motorcycles when police stopped ambulances from entering."
Neighboring oil giant Saudi Arabia and the United States fear escalating violence could push impoverished Yemen, already riven by tribal and separatist conflict, into chaos that could allow al Qaeda's Yemen-based wing to operate freely.
Demonstrators have sought to shut down some of Yemen's major cities and many have called for a daily general strike.
In Taiz, security forces have shot dead six protesters in three days of clashes. Authorities were struggling unsuccessfully to break up a protest blockade on the education ministry, part of a siege of state buildings that has effectively brought Yemen's main industrial center to a halt.
"Stores are closed and the streets are completely empty of pedestrians, only protesters are around in the areas they are confronting (security forces)," resident Wajdi Abdullah said.
Protesters also brought life to a halt in the city of Ibb. "Almost all the stores are shut in Ibb except a few selling basic food items. No one is going to work — this is unprecedented in this city," resident Ali Noaman said.
Tribesmen aligned with protesters have blockaded Yemen's main oil- and gas- producing province Maarib, causing a mounting fuel crisis. A shipping source told Reuters the government was losing around $3 million a day in blocked exports.
Traders said on Wednesday Yemen was in talks with Saudi Aramco to buy around 2 million barrels of crude oil to send to its main refinery in Aden, shut for weeks due to lack of supply.
The protesters' pressure on oil supplies has made petrol scarce and led to power cuts. Fuel rationing has worsened water shortages in remote areas where trucks have stopped deliveries.
Yemen's fragile economy is struggling to stay afloat as the currency tumbles and prices of necessities soar. A third of Yemen's 23 million people suffer chronic hunger and 40 percent live on less than $2 a day.