(New York) - Negotiators should immediately remove a promise of immunity from any resignation deal for President Ali Abdullah Saleh of Yemen in light of repeated, lethal attacks by his security forces on peaceful protesters, Human Rights Watch said today. In the latest attacks, security forces, along with pro-government gunmen in civilian clothing, have shot dead at least 21 people since May 7, 2011 - at least 15 of them on May 11 and 12 - and wounded hundreds.

After weeks of delay, Saleh agreed on April 23 to a pact brokered by the Gulf Cooperation Council (GCC) and backed by the United States and the European Union, in which he would resign within 30 days in exchange for blanket immunity for himself, government officials, and close relatives who include commanders of security forces that have repeatedly fired on protesters. The broad language in the pact appears to set no limits on the immunity terms. But Saleh has stalled on signing, demanding additional changes or concessions, as security forces continue shooting at peaceful protesters.

"These attacks suggest that President Saleh views his promise of immunity as a ‘Get Out of Jail Free' card for political murder," said Joe Stork, deputy Middle East director at Human Rights Watch. "The GCC member states and other governments involved in negotiations for President Saleh's exit should immediately pull immunity from the table."

Yemeni courts and foreign governments will still be obligated to hold Saleh to account for the attacks even if an immunity deal is signed, Human Rights Watch said.

International law rejects impunity for serious crimes, such as crimes against humanity and torture, Human Rights Watch said. International treaties, including the Convention against Torture, and the Rome Statute of the International Criminal Court, require states parties to ensure that alleged perpetrators of serious crimes are prosecuted, including those who give the orders for these crimes. Systematic or widespread unlawful killings, carried out as a state policy, are likely to be crimes against humanity.

At least 137 people have died in attacks by security forces and pro-government assailants on anti-Saleh protesters since February.

In the latest attacks, on May 11 and 12, security forces and pro-government gunmen shot dead protesters in the capital, Sanaa, and provincial cities including Taizz, the western port city of al-Hudaida, and the central city of al-Baida'. Many of the protesters were shot as they tried to occupy or blockade government buildings, witnesses told Human Rights Watch. Yemeni officials blamed the opposition for the violence, saying demonstrators were trying to "storm" government buildings, but numerous witnesses said the protesters were not using any form of violence.

"Security forces are only allowed to use lethal force when lives are at stake, and that does not appear to have been the case in these incidents," Stork said.

In Sanaa on May 11, security forces and gunmen in civilian clothing opened fire after protesters started marching toward the prime minister's office, human rights activists and a doctor at the scene told Human Rights Watch. Witnesses said security forces fired hundreds of rounds of live ammunition over several hours, killing at least 11 protesters and wounding about 230. The security agents who opened fire included members of the Central Security and General Security forces, witnesses said.

Shortly before the shooting, some protest leaders had been urging marchers to surround the prime minister's building, witnesses said. They said the protesters did not appear to be armed.

In Taizz, a city south of Sanaa, security forces shot dead seven protesters and wounded dozens during peaceful demonstrations from May 7 through 12, witnesses and doctors told Human Rights Watch. Protesters on May 11 responded by taking over three government buildings and large swaths of the city, in some cases blocking streets with burning tires. That day, for the first time, some anti-Saleh protesters carried weapons, including Kalashnikov assault rifles and handguns, witnesses said. However, the same witnesses said that at no time did they see any of the anti-Saleh protesters firing the weapons.

Central Security forces shot dead one protester in Taizz when they opened fire to disperse a peaceful demonstration on May 7, witnesses told Human Rights Watch. The rest of the recent killings in Taizz took place after striking teachers surrounded the city's Education Ministry on May 8 to demand unpaid wages, witnesses said. Many teachers in Yemen had joined the anti-Saleh protests and went on strike in mid-March to demand benefits to which they said they were entitled under a 2005 law. The government froze the teachers' wages in response.

After a local official promised to address their grievances if they dispersed, the teachers and their supporters began leaving the square, but gunmen from forces including Central Security, Republican Guards, and General Security fired on them as they retreated, killing two, several witnesses said.

Those deaths prompted larger protests in Taizz the following day, in which anti-Saleh demonstrators blockaded the Education Ministry after workers inside had fled. The protesters were not violent, but security forces again opened fire to disperse them, killing three people, witnesses said. Security forces killed another protester on May 11 after demonstrators again blockaded the Education Ministry, and wounded at least 20 more on May 12 when they opened fire and sprayed teargas on protesters staging a sit-in outside a Taizz school.

In al-Hudaida, Republican Guards firing at protesters from the top of a government building killed one man on May 11.

In al-Baida', gunmen dressed in civilian clothes on May 12 shot dead two protesters and wounded seven as they fired on an anti-Saleh demonstration from the local headquarters of the ruling party, the General People's Congress.

Foreign donors - including EU member states meeting on May 13 in Brussels - should immediately suspend all direct and indirect military assistance and weapons sales to Yemen to pressure Saleh to put an end to the attacks, Human Rights Watch said. Countries should not resume military aid and weapons sales unless Yemeni authorities stop the use of lethal force in circumstances where lives are not threatened, conduct independent investigations into the killings, prosecute suspected perpetrators, and compensate victims.

Donors also should press the United Nations Human Rights Council to explicitly address the escalating human rights crisis in Yemen.

"The latest round of attacks suggests that President Saleh has no intention of ending the daily abuses of human rights," Stork said. "It is high time for foreign donors to stop indulging a government that routinely resorts to deadly force to stay in power."