Friday sees the biggest day of protest in Yemen thus far…

Unidentified gunmen killed four soldiers on patrol in the southeastern city of Hajarain, a local official said.

A wave of unrest, inspired partly by popular revolts in Egypt and Tunisia, has weakened Saleh’s 32-year grip on his impoverished nation, a neighbor of oil giant Saudi Arabia and home to an agile and ambitious regional al Qaeda wing.

Yemenis flooded streets and alleys around Sanaa University in the biggest protest to hit the capital since demonstrations began in January. About 30 people have been killed since then.

But tens of thousands of Saleh loyalists also crammed Sanaa’s Tahrir Square, touting pictures of the veteran leader.

“Your duty is to guard stability, I know many of you are suffering economic hardship, but we Muslims are different. Income comes from God and prayer,” a preacher told them.

Reuters reporters put the Sanaa turnout at more than 40,000. Tens of thousands marched in Taiz and Ibb, south of the capital.

“We want him to go”

The protesters gave short shrift to Saleh’s offer on Thursday of a new constitution to be voted on this year and electoral reforms.

“We don’t want initiatives, we want him to go,” said one demonstrator, Ali Abdulrahman.

Tribesman Mohammed Saleh said: “All of us tribes are here now to demand that this guy leaves. We’re tired of him.”

Several of Yemen’s influential tribes have turned against Saleh, as have some Muslim clerics and ruling party lawmakers.

“It is only a matter of time before we see mass civil disobedience,” said a senior government official, who asked not to be named. “Saleh will likely declare emergency law, but I do not think he will survive.”

As Yemen’s water and oil resources dry up, it has become increasingly difficult for Saleh, 68, to fuel the patronage system that kept his tribal and political supporters loyal.

In the central province of Maareb, residents said hundreds of Yemenis demonstrated because they had not been paid for attending Saleh’s speech in Sanaa on Thursday.

The local newspaper Maareb Press said they been promised 50,000 Yemeni riyals ($233) and began shouting “the people demand the fall of the regime” when they did not get the money.

Protesters want an end to Saleh’s autocratic system, in which his relatives and allies hold key posts. They also cite frustration with rampant corruption and soaring unemployment.

Chronic hunger

Some 40 percent of Yemen’s 23 million people live on less than $2 a day and a third face chronic hunger.

The office of the U.N. High Commissioner for Human Rights on Friday called on Yemen’s government to investigate alleged killings of pro-reform demonstrators.

“We call on the government to exercise restraint and to investigate all allegations of extrajudicial killings and human rights violations at the hands of the security forces,” said spokesman Rupert Colville.

“The office is very concerned by allegations of the excessive use of force by some security forces,” he added.

Colville said about 37 protesters and at least six security officers had reportedly been killed since the unrest started in Yemen.

The killings highlighted by the U.N. human rights office included those of two demonstrators at Sanaa University on Mar. 9, the deaths of two or three prisoners in riots at Sanaa central prison on Mar. 8 and the alleged killing of two protestors on Mar. 4 near the town of Harf Sufyan, in the northern province of Amran.

The U.S. ambassador, in an interview with a state-backed magazine to be published on Saturday, encouraged protesters to engage in dialogue with the government on Yemen’s future.

“Our question is always, if President Saleh leaves, then what do you do on the next day?” asked Gerald Feierstein.

The United States fears that Saleh’s overthrow might lead to a power vacuum that would be exploited by Islamist militants in the Arabian Peninsula state, from which al-Qaeda has launched attacks on Western and Saudi targets.