The wires are now reporting that Yemeni security forces opened fire on tens of thousands of anti-government protesters  in the capital, Sannaa, on Wednesday, killing one person and injuring at least 40 more, according to the AP. There are also reports of deaths in the southern city of Taiz and nearby Damar after clashes with security forces, and demonstrations in several other locations.

The AP, citing witnesses, paints a vivid picture of the violence in Sanaa, noting how protesters marching from a main square in the city toward the cabinet's headquarters "came under fire from snipers on rooftops, plainclothes security forces, and soldiers with anti-aircraft guns mounted on pickup trucks," with security forces also employing water cannon and tear gas. Some protesters who hopped on motorcycles to find treatment for injured protesters were stopped by officers, who loaded the injured into police vehicles.

Reuters takes us to Taiz, where "the daily rhythms of Yemen's main industrial center" are at a standstill. "Dozens of protesters were wounded by gunfire, tear gas and beatings by bat-wielding plainclothes security men," the news outlet reports, and protesters responded by lighting a police building on fire, storming government buildings, and burning tires (see above). The AFP adds that demonstrators locked the gates of the Yemen Petroleum Company with chains and posted a sign: "Shut by the people." This video, via NPR's Andy Carvin, allegedly shows the protesters seizing the police station:

Another video from Taiz highlighted by Carvin seems to capture security forces firing heavy weapons from trucks:

As a Gulf Cooperation Council plan for Yemeni President Ali Abdullah Saleh to step down within 30 days flounders, Reuters points out that the country is simultaneously grappling with a mounting fuel crisis. Tribesman who support the protesters have blockaded Yemen's primary oil- and gas-producing Maarib province, forcing the government to turn to Saudi Arabia for crude oil. The country's currency is plummeting as the prices of necessities soar and remote areas experience water shortages. These crises, coupled with the mounting violence, are creating an increasingly dangerous situation in a fragmented, impoverished country in which, as Reuters points out, "half the population owns a gun." Meanwhile, Yemen-based Al-Qaeda in the Arabian Peninsula warned today that, in the wake of Osama bin Laden's death, the "ember of jihad is brighter," according to AFP.

Update: NPR's Andy Carvin has a steady stream of amateur videos out of Yemen. This one shows people running en masse from gunfire: