SANAA, Yemen -- The United Nations High Commissioner for Human Rights has expressed “deep concern” over increasing attacks against civilians in Yemen with a total of 180 civilians killed in one month, raising the death toll to nearly 4000 since March 2015.

Cecile Pouilly at the UN agency said on Friday that August also marked an increase in the number of attacks against civilian facilities including hospitals, markets, and places of worship.

Her statement came only two days after airstrikes by the U.S.-backed Saudi-led coalition bombed houses in the Red Sea port city of Hodeidah, killing at least 32 civilians.

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Meanwhile, rebels known as Houthis have continued to tighten their siege on the city of Taiz, where they are fighting local forces aligned with the internationally-recognized government.

The U.S. Senate on Wednesday backed the Obama administration’s plan to sell more than $1 billion worth of American-made tanks and other weapons to Saudi Arabia, soundly defeating a bid to derail the deal pushed by lawmakers critical of the kingdom’s role in Yemen’s civil war.

Senators who supported the sale said the United States can’t deny its Middle East allies the weapons they need to combat Islamic State of Iraq and Syria (ISIS) extremists and check Iran’s aggression in the region.

“Blocking this sale of tanks will be interpreted by our Gulf partners, not just Saudi Arabia, as another sign that the United States of America is abandoning our commitment to the region and is an unreliable security partner,” said Sen. John McCain, R-Ariz., the chairman of the Senate Armed Services Committee.

Although a resolution against the sale failed to advance on a vote of 71-27, the measure’s sponsors said the debate demonstrated that congressional support for arms sales -- even to a longtime and important Middle East ally -- isn’t automatic. They also used the time to insist that Congress play a larger role in foreign policy decisions, especially those involving the use of military force.

The war in Yemen is pitting the country’s internationally recognized government and a Saudi-led coalition against the Shiite rebels known as Houthis, who are allied with army units loyal to a former president. The Saudi-led coalition has been carrying out airstrikes in Yemen since March 2015 and thousands of civilians have been killed in the fighting, according to the U.N. human rights chief.

The United States is supporting the Saudi-led coalition with intelligence and logistical support, including refueling aircraft, according to senators opposed to the sale. Most Americans are unaware of how involved their military is in Yemen, they said, adding that lawmakers never have fully discussed whether the participation advances U.S. national security interests.

“Should Congress just lie down and be a lapdog for the president?” asked Sen. Rand Paul, R-Ky., a sponsor of the resolution. “Everyone should understand that this is a proxy vote for whether we should be at war in the Middle East.”

Sen. Chris Murphy, D-Conn., who also opposed the sale, said the Saudis have bombed areas that the U.S. has asked them to avoid. At the same time, the ISIS and al Qaeda are growing “by leaps and bounds,” Murphy said, because the Saudis are hitting primarily Houthi and civilian targets.

“Let’s press the Saudis to get serious about spending more time as firefighters and less time as arsonists in the global fight against terrorism,” Murphy said.

The American Bar Association said last week there are credible reports Saudi forces have used American-made military equipment to carry out “indiscriminate and disproportionate” attacks on civilians.

The U.S. should suspend further security assistance to Saudi Arabia “at least until such time as it can be credibly determined” that the allegations have been investigated and the kingdom is abiding by the law of armed conflict, the director of the bar association’s governmental affairs office said in a Sept. 14 letter to Murphy and Paul.

The Defense Department informed Congress of the proposed $1.15 billion sale to Saudi Arabia on Aug. 8. The deal involves more than 100 main battle tanks, machine guns, smoke grenade launchers, night-vision devices, vehicles to recover damaged tanks from the battlefield, and thousands of rounds of training ammunition.

The primary contractor for the equipment is General Dynamics Land Systems of Sterling Heights, Michigan.

U.N. human rights chief Zeid Ra’ad al-Hussein last month called for an international investigation of rights abuses and violence in Yemen. His Geneva office released a 22-page report that chronicled abuses on both sides in the conflict.

Roughly 3,799 civilians had been killed since the air campaign began, according to Zeid’s report. The U.N. and rights groups estimated at least 9,000 people overall have died. Nearly 3 million more people have also been displaced inside the Arab world’s poorest country.

Airstrikes by the Saudi-led coalition were responsible for 60 percent of the 2,067 civilians killed in the conflict over a yearlong span starting on July 1, 2015, according to the report. Just under one-quarter - 475 - of the civilian deaths were attributed to rebel forces like those loyal to former President Ali Abdullah Saleh, and 113 to affiliates of al Qaeda and ISIS.