Commissioner Bud Selig requested on Friday that all Major League clubs in the U.S. fly their flags at half-staff through sunset on Sunday, in support of the government response as the nation mourns the slaying of four Americans this week in Libya.

The bodies of ambassador Christopher Stevens, former Navy SEALs Glen Doherty and Tyrone Woods and Air Force veteran Sean Smith returned to American soil on Friday after the four were killed in an attack on a diplomatic mission in Benghazi on the 11th anniversary of the Sept. 11 attacks.

"I hereby order that the flag of the United States shall be flown at half-staff at the White House and upon all public buildings and grounds," President Obama said in a proclamation.

The order applies to all U.S. military posts, diplomatic sites abroad and ships at sea and will remain in force until sunset on Sunday, for five days of observance in recognition. The order is not binding on private businesses, but Selig took the action Friday to demonstrate the national pastime's support of the President's request.

At Target Field, where the Twins began a weekend series against the White Sox, the three flagpoles in right field -- bearing the flags of Hennepin County, the U.S. and prisoners of war and Twins Territory -- all had their flags at half-staff.

On Saturday and Sunday at Marlins Park, the American flag there will be lowered. The flag is located beyond the wall in left-center field, next to the home run sculpture.

"As everyone else in baseball, our thoughts and prayers are with those families affected by these tragedies," said P.J. Loyello, the Marlins' senior vice president of communications and broadcasting.

In addition to lowering their flags, the Yankees offered a moment of silence prior to their first pitch Friday against the Rays. Across the country at Petco Park in San Diego, a major Navy town where military personnel and family typically fill many of the seats, the flags were lowered for the start of a Padres series against Colorado. The scene was similar elsewhere at stadiums like Minute Maid Park in Houston, where the flags beyond center field were dropped amid the game against Philadelphia.

The one Major League club outside of the U.S. is in Canada, where the Red Sox played in Toronto. The flags at Rogers Centre are permanent fixtures attached to a section of the roof and cannot be lowered to half-staff.

Braves manager Fredi Gonzalez said the killings in Libya were the latest example of people not valuing the lives of other humans.

"It's sad that the world is in that state," Gonzalez said. "People all over the world, even here in the United States, there are some acts that are mind-boggling. It's just sad."

"The United States condemns in the strongest terms this outrageous and shocking attack," Obama said in a statement in the White House Rose Garden. "Make no mistake, we will work with the Libyan government to bring to justice the killers who attacked our people."