AP Top News at 2:30 a.m. EDT

By Associated Press,

GREER, S.C. — Republican presidential contender Mitt Romney declared Thursday he has paid at least 13 percent of his income in federal taxes every year for the past decade, offering that new detail while still decrying a “small-minded” fascination over returns he will not release. President Barack Obama’s campaign shot back in doubt: “Prove it.” Campaigning separately, Romney and running mate Paul Ryan also scrambled to explain their views on overhauling Medicare, the health care program relied on by millions of seniors.

BEIJING — The powerful uncle of North Korean leader Kim Jong Un met with both President Hu Jintao and Premier Wen Jiabao on Friday morning, after Beijing earlier in the week agreed to help Pyongyang revamp two trade zones near the Chinese border. The high-level talks are a sign that Beijing and Pyongyang are strengthening ties after Kim took over following his father’s death last year. State media have said the visit by Jang Song Thaek, the chief of the central administrative department of the Workers’ Party of Korea, is a possible prelude to a visit by Kim himself. China remains North Korea’s most important ally.

LONDON — He’s won asylum in Ecuador, but Julian Assange is no closer to getting there. The decision by the South American nation to identify the WikiLeaks founder as a refugee is a symbolic boost for the embattled ex-hacker. But legal experts say that does little to help him avoid extradition to Sweden on sexual assault allegations.

JOHANNESBURG — South African police officers killed more than 30 striking workers at a Lonmin PLC platinum mine who charged a line of officers trying to disperse them, authorities said Friday. The shooting Thursday is one of the worst in South Africa since the end of the apartheid era.

PITTSBURGH — In a surprising turnaround, the amount of carbon dioxide being released into the atmosphere in the U.S. has fallen dramatically to its lowest level in 20 years, and government officials say the biggest reason is that cheap and plentiful natural gas has led many power plant operators to switch from dirtier-burning coal. Many of the world’s leading climate scientists didn’t see the drop coming, in large part because it happened as a result of market forces rather than direct government action against carbon dioxide, a greenhouse gas that traps heat in the atmosphere.

WASHINGTON — President Barack Obama and Republican rival Mitt Romney agree there has to be a limit to how much seniors pay for Medicare, but they’re worlds apart on how to make that happen. You wouldn’t know it from the accusations they hurl on the campaign trail, but that is the real heart of the argument between the two leaders and their political parties.

WASHINGTON — Sarah Palin and George W. Bush won’t be in Tampa, Fla. Hillary Rodham Clinton and Al Gore won’t make the trip to Charlotte, N.C. And scores of other Republican and Democratic stars are taking a pass as their parties gather for this year’s national conventions. The reasons are varied — and often, of course, political.

KABUL, Afghanistan — A U.S. military helicopter crashed during a firefight with insurgents in a remote area of southern Afghanistan on Thursday, killing seven Americans and four Afghans in one of the deadliest air disasters of a war now into its second decade. The Taliban claimed they gunned down the Black Hawk. American service personnel in Afghanistan are dying at a rate of about one per day so far this year despite a drawdown of troops. That death rate has risen recently with the summer fighting season in full gear and a rash of attacks by Afghan security forces on their foreign trainers and partners.

CHICAGO — U.S. Rep. Jesse Jackson Jr. is in a “deep” depression and has “a lot of work” ahead of him on the road to recovery, former Rhode Island U.S. Rep. Patrick Kennedy said Thursday after visiting the hospitalized Chicago Democrat. Jackson has been on a secretive medical leave since June 10, when family members said he collapsed at their home in Washington. He is currently being treated for bipolar disorder at the Mayo Clinic in Rochester, Minn. But neither his office nor family members have said much about his medical condition.

FRESNO, Calif. — A 10-year-old boy died and his 6-year-old brother was missing after they were swept away along a popular but treacherous boulder-strewn stretch of the Merced River, Yosemite National Park officials said Thursday. The two victims were part of a family visiting from Southern California that was hiking near the Vernal Fall Footbridge. Group members were cooling off in the river Wednesday when a current carried the boys away.