FARAH, Afghanistan, July 20 (UPI) -- Nine police officers were killed by friendly fire in southwestern Afghanistan Sunday, military officials said.

An Afghan army general said the police were mistaken for Taliban militants and died in an airstrike conducted by U.S and Afghan forces in the country's Farah province, CNN reported. The deaths came one week after a similar friendly fire episode killed eight civilians in the same province.

Four civilians died and four were wounded in a second weekend incident when NATO-led troops fired mortar rounds in southeastern Afghanistan's Paktika province, CNN said.

KABUL, Afghanistan, July 20 (UPI) -- Likely U.S. Democratic presidential nominee Barack Obama had breakfast with U.S. troops in Afghanistan Sunday before meeting with the the country's president.

Sen. Obama, D-Ill., ate his meal in the mess hall of an American military base in Kabul as he prepared for his first meeting with President Hamid Karzai, whose policies he has criticized in the past, CNN reported.

Obama arrived in eastern Afghanistan Saturday with two other U.S. Senators, Chuck Hagel, R-Neb., and Jack Reed, D-R.I., both of whom have been mentioned as his possible running mates.

Meanwhile, Obama's likely Republican presidential opponent, U.S. Sen. John McCain, R-Ariz., criticized him for going to Afghanistan with his anti-terrorism policies already decided.

In a time of war, the commander in chief's job doesn't get a learning curve, McCain said Saturday in a radio address.

MOGADISHU, Somalia, July 20 (UPI) -- Foreign aid workers trying to stave off a famine in Somalia say assassinations and kidnappings are forcing them to flee the country.

At least 20 aid workers have been killed since January and 17 have been abducted, The New York Times reported Sunday. Leaflets warning aid workers they're being targeted for further assassinations are prompting many to flee dangerous urban areas such as Mogadishu and the situation is endangering United Nations food relief efforts.

The aid worker killings appear to be well organized and some blame violently anti-Western Islamic militant groups opposed to the country's embattled central government. But the leader of one such group denied the claims, telling The Times his group is guarding foreign aid workers, not killing them.

Another theory is that government agents are slaying and kidnapping the workers in order to make the situation so bad, U.N. peacekeeping forces will be drawn into Somalia's civil war. But the government denies this, the Times said.

It's obvious who's doing this, Abdi Awaleh Jama, a Somali ambassador at large, told the newspaper. It's hard-liner Islamists who hate the West. They are forces of darkness, not forces of light.

WASHINGTON, July 20 (UPI) -- Political observers say both the likely major party U.S. presidential nominees are in the final phases of picking their vice presidential running mates.

U.S. Sen. Barack Obama, D-Ill., is looking to avoid any risky or potentially costly mistakes in making his choice, while the opposite is true for U.S. Sen. John McCain, R-Ariz., who needs someone to change the political equation for him, analysts said in Sunday's edition of The New York Times.

Republicans need to do something to shake things up, Steve Elmendorf, a former aide to U.S. Sen. John Kerry, said. Barack is in a different situation, and he needs somebody who can be safe and steady.

Among those considered to still be under Obama's consideration are Sens. Evan Bayh, D-Ind., and Joseph Biden, D-Del.; former Democratic Senator Sam Nunn; and Virginia Gov. Tim Kaine. McCain is looking at former GOP presidential rival Mitt Romney; Minnesota Gov. Tim Pawlenty and Florida Gov. Charlie Crist.

McCain needs to pick someone who will really energize and excite the party, but also someone with whom McCain feels a real comfort level and is young enough for those worried about the age issue, Republican strategist Ed Rollins told The Times.