SANAA/ADEN, (Reuters) – Factional fighting in

Yemen’s north entered its fifth day on Tuesday, bringing violence closer to the border with Saudi Arabia, while the United States’ top counter-terrorism official visited Sanaa.

Twenty-three people have been killed and dozens injured in the northern province of Jawf since clashes broke out on Friday between members of Yemen’s main opposition party Islah and northern Shi’ite rebels known as Houthis.

Jawf lies along Yemen’s northern border with oil giant Saudi Arabia, which fears that unrest in its poverty-stricken southern neighbour could spill over and create a major security threat.

Fighting started when Houthis refused to give up an army base they occupied after the governor of Jawf fled two months ago, an opposition source said.

Saudi Arabia launched a military offensive against the Houthis after they briefly seized Saudi territory in late 2009. Houthi rebels have fought President Ali Abdullah Saleh’s government on and off since 2004.

Protests against Saleh’s 33-year rule had united Houthis and protesters, including the Sunni Muslim Islah, but rifts have begun to appear as a political stalemate drags on.

Saleh left Yemen in political limbo when he flew to Saudi Arabia to seek treatment after he was severely injured by a bomb attack in the presidential palace in early June.

Before that, as protests against his rule raged, Saleh had three times rejected a transition deal brokered by Gulf Arab states, and held on to power.

U.S. ENVOY MEETS SALEH

U.S. envoy John Brennan, who met Saleh in Riyadh on Sunday to urge him to accept a transition plan, was in the capital Sanaa to meet the leader of the main opposition bloc.

“We met with Brennan and there was nothing new in the American stance,” said opposition leader Abu Bakr al-Badhib.

“He told us the president intends to return soon and that the Americans are not in favour of this, but he is resolved and says his return will help to pacify matters.”

In southern Yemen, which has borne the brunt of the crisis, at least two pro-opposition tribal gunmen were killed in clashes with forces loyal to Saleh in the city of Taiz, Al Jazeera television said.

Heavy fighting continued late into the night, with pro-Saleh forces using mortars, artillery and tanks in the city, the site of large anti-government protests, it said.

“There is artillery fire, and heavy explosions can be heard. This has become a daily occurrence in Taiz, terrorising the inhabitants,” Al Jazeera correspondent Hamdi al-Bakari said.

Earlier, 11 militants were killed in military strikes in the south while clashes within the police force over delayed salary payments injured three.

Five Islamist militants were killed in air strikes on Abyan province on Tuesday, where six were killed in a battle late on Monday, local government officials said.