A faction of Yemen's separatist Southern Movement on Saturday called for a day of "civil disobedience" to disrupt next week's presidential election.

The Higher Council of the Peaceful Movement for the Liberation of the South, in a statement, called on its supporters to "take every possible peaceful action" against Tuesday's election to prevent it going ahead.

Yemen's President Ali Abdullah Saleh, who is due to step down next month, arrived Saturday in the United States on a politically sensitive visit to seek medical treatment for wounds inflicted in a bombing.

The embattled leader flew from Oman to the United States with a brief refueling stop at Stansted Airport outside London, ending days of speculation about whether or when he would make the trip.

Al-Qaida gunmen have withdrawn completely from the central Yemen town of Rada, which they overran nine days ago, tribal sources and witnesses said on Wednesday.

"They have left the town," located 130 kilometers (85 miles) southeast of Sanaa, one tribal source said hours after a senior military official said there had been mediation to convince them to withdraw.

Forces loyal to Yemeni President Ali Abdullah Saleh shot dead a woman and wounded six other people when they opened fire on a crowd of protesters in the city of Taez on Monday, medics said.

The protest was over an immunity clause in the Gulf-sponsored transition plan which Saleh signed last month to hand power over to his deputy, Vice President Abdrabuh Mansour Hadi.

Loyalists of Yemeni President Ali Abdullah Saleh shot dead five people in Sanaa on Thursday who had been protesting against a power transfer deal that promises him immunity from prosecution, medics said.

The five were all killed by live rounds, said the medics at a field hospital set up protesters in the capital's Change Square, where they have been camped out since February.

Forces loyal to President Ali Abdullah Saleh clashed Wednesday with dissident tribesmen in the Yemeni capital, residents said, while the veteran leader was in Riyadh to sign a power transfer deal.

The clashes broke out between gunmen loyal to dissident tribal chief Sheikh Sadiq al-Ahmar and pro-Saleh troops in al-Hasaba district, while explosions were heard in the nearby neighborhood of Sufan, residents there said.

Operations at Aden's refinery came to a complete halt as crude oil supplies dried off after a pipeline was attacked in the latest act of sabotage on oil and gas installations in Yemen, a company official said Monday.

"The company's operations have stopped due to the lack of crude oil," said an official from the government-owned Aden Refinery Company.

Fierce clashes erupted in Yemen's second city Saturday as protesters in the capital Sanaa condemned international silence in the face of a government crackdown that left more than 15 dead the previous day.

"Oh world, the children and women of Taez are being killed...where is your conscience?" chanted tens of thousands of protesters in Sanaa who for 10 months now have been calling for President Ali Abdullah Saleh to step down.

One person died and several were hurt in clashes Thursday in the flashpoint city of Taez and the capital Sanaa during protests calling for Yemeni President Ali Abdullah Saleh's prosecution, medics and witnesses said.

The bloodletting came as U.N. envoy to Yemen Jamal Benomar arrived in Sanaa in an attempt to resolve the political crisis that has thrown the country into a spiral of violence in which hundreds have died since January.

At least 12 people have been killed and more than 40 others wounded in renewed clashes in Yemen's capital and its second city, medics and activists said on Wednesday, after a brief period of calm.

Armed clashes broke out early Wednesday in the flashpoint city of Taez between government forces and tribesmen who support a mass protest movement calling for President Ali Abdullah Saleh's resignation, said activists.