ISLAMABAD — The Pakistani government said Wednesday that three percent of the people killed in U.S. drone strikes in the country since 2008 were civilians, a surprisingly low figure given past official calculations and estimates from independent organizations.

The Ministry of Defense provided the data in a written response to questions from the Senate, saying 317 attacks have killed 2,160 Islamic militants and 67 civilians since 2008.

The strikes are very unpopular in Pakistan, where many people believe they violate the country's sovereignty and kill too many innocent civilians. The Pakistani government regularly criticizes the attacks in public, even though it is known to have secretly supported at least some of the strikes in the past.

It's unclear how the new casualty information will affect the drone debate in the country.

A U.N. expert investigating drone strikes said earlier this month that the Pakistani government told him that at least 400 civilians have been killed by the attacks in the country since they started in 2004.

The Bureau of Investigative Journalism, based in London, has estimated that at least 300 civilians have been killed by drones in Pakistan since 2008. The Washington-based New America Foundation put the figure at 185 civilians. These estimates are often compiled based on media reports about the attacks.

The U.S. considers the CIA-run drone program in Pakistan to be a key weapon against al-Qaida and also Taliban militants who stage cross-border attacks against American troops in neighboring Afghanistan. The U.S. rarely speaks publicly about the program because it is classified. But officials have insisted in private that the strikes have killed very few civilians and the estimates from independent organizations are exaggerated.

Amnesty International called on the U.S. to investigate reports of civilians killed and wounded by drone strikes in Pakistan in a report released earlier this month that provided new details about the alleged victims of the attacks, including a 68-year-old grandmother killed while farming with her grandchildren.

Mamana Bibi's grandchildren told the London-based rights group that she was killed by missile fire on Oct. 24, 2012, as she was collecting vegetables in a family field in the North Waziristan tribal area, a major militant sanctuary near the Afghan border. Three of Bibi's grandchildren were wounded in the strike, as were several others who were nearby, the victims said.

An even deadlier incident noted by the report occurred in North Waziristan on July 6, 2012. Witnesses said a volley of missiles hit a tent where a group of men had gathered for an evening meal after work, and then a second struck those who came to help the wounded, one of a number of attacks that have hit rescuers, the rights group said.

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Witnesses and relatives said that total of 18 male laborers with no links to militant groups died, according to Amnesty. Pakistani intelligence officials at the time identified the dead as suspected militants.

Contrary to the information outlined in the report, the Pakistani government said Wednesday that there were no civilian casualties in 2012. The government said 21 civilians were killed in 2008, nine in 2009, two in 2010 and 35 in 2011. No civilians have been killed so far in 2013, the government said.