Anti-government protesters shout slogans during a rally to demand the ouster of Yemen's President Ali Abdullah Saleh in Sanaa June 1, 2011. [Agencies]

SANAA, Yemen - Street battles between Yemeni government forces and armed tribesmen killed dozens of people Wednesday in this country teetering on the brink of civil war, forcing residents to cower in basements or brave gunfire to fetch bread and water.

Nearly four months of mass protests calling for President Ali Abdullah Saleh's ouster have exacerbated already dire poverty, shuttering businesses and forcing up prices of essential goods. It's a trend that does not bode well for long-term stability in this gun-ridden corner of the Arabian Peninsula, home to an active al-Qaida branch and other armed Islamist groups.

Yemen's mainly peaceful protests gave way to fighting last week between Saleh's security forces and fighters loyal to the head of Yemen's most powerful tribal coalition, Sheik Sadeq al-Ahmar. That was the tipping point that pushed the anti-government uprising toward civil war.

At least 41 people were killed Wednesday as clashes spread to new quarters of the city.

Fighting in the capital raged from early morning though midday, sending the crackle of gunfire and the booms of artillery strikes across the city. The clashes spread Wednesday from the Hassaba neighborhood where tribesmen have seized more than a dozen government buildings, to new areas.

The clashes forced Talal Hazza to crowd into a neighbor's basement with 20 others, half of them children.

"We are suffering and living through trying days," Hazza said. "It wears you out because the shells fall on us like rain, especially at night."

The explosions terrify the children, and only the men go out for food, Hazza said. They have to venture out daily because the area has had no electricity for two days, meaning there is no way refrigerate food.

"We can hear explosions outside, but we are afraid to go up and look because they are very close," he said.

Tribal fighters seized the prosecutor general's office in the city's northwest. They were accompanied by two vehicles from the 1st Armored Division, whose powerful commander abandoned Saleh two months ago. So far, however, his troops have not participated in the street battles.

The Interior Ministry said in a statement that tribesmen also took over a five-story building in the city's southern Hadda neighborhood, a stronghold of Saleh supporters.

Yemen's official news agency SABA called the tribal fighters "armed gangs" and accused them of looting supplies, furniture and documents from government buildings.

Witnesses said units of the elite Presidential Guard, commanded by one of Saleh's sons, shelled the headquarters of an army brigade that guards government institutions, sending up columns of smoke and fire. Army officers who have joined the opposition said they believed the move was a pre-emptive strike against a commander the government feared would join the movement to oust Saleh.

Fighting diminished in the afternoon, when Yemenis routinely gather to chew qat, a mildly addictive stimulant. But artillery strikes resumed at dusk, forcing residents back to their basements.

"We feel besieged in our neighborhood and can't leave our house because of the clashes and the random shelling," said resident Abdu Salem. A shell landed near his house, spraying his neighbor's leg with shrapnel, Salem said, but the clashes prevented an ambulance from coming for four hours.

As the uprising has dragged on, prices for food, petrol and cooking gas have skyrocketed, cutting into family budgets in a country where the United Nations says 31 percent of people are underfed.

Experts say growing poverty and a depleted government budget heighten the chances of longtime instability in a nation that is home to al-Qaida in the Arabian Peninsula, which has been linked to attempted attacks on US soil, including the failed Christmas Day attack in 2009.

"We're already talking about the poorest country in the Arab world, and the average Yemeni has the least room to absorb this," said Christopher Bouceck of the Carnegie Endowment for International Peace. "The longer this goes on, the worse it gets."

Shopkeeper Najib al-Habaishi said his foodstuffs are scarce and his prices high because distributors balk at delivering to the capital.

Running water has cut out in much of the capital, meaning residents buy supplies from tanker trucks. But the price of a fill up has quadrupled during the uprising, forcing many to limit bathing and laundry to once a week.

The price of cooking gas, too, has increased steeply, meaning some many now light wood fires on their roofs to cook.

Rising gas prices have caused shortages, forcin

g people to wait for hours in long lines at gas stations. Once at the pump, they face quotas that limit them to about a third of a tank.

Electricity comes and goes, and has been cut in the Hassaba neighborhood for nearly three days.