Concern about mass South Korean street protests are reaching the highest possible level, with South Korea's president phoning the White House to express his concern.  Many demonstrators are rejecting attempts by the two leaders to address concerns about a U.S. beef import deal.  Meanwhile local hospital officials say at least six demonstrators and several police officers suffered injuries in street violence today. Police say they have made at least 11 arrests.  VOA's Kurt Achin reports from Seoul.

President George Bush has told South Korean President Lee Myung-bak he will try to help address South Koreans' health concerns about beef from U.S. cattle of a certain age.

The presidential Blue House in Seoul said Mr. Lee telephoned President Bush Saturday night to discuss the anxiety tens of thousands of South Korean protesters have been taking to the streets almost every night for about a month now.  The protesters are especially concerned about beef from cattle more than two and a half years old, which they perceive to carry a risk of the fatal brain condition known as "mad cow disease."

A Blue House statement Sunday said Mr. Bush assured the South Korean president his administration would "come up with concrete measures aimed at preventing beef from cattle more than 30 months' old from being shipped to South Korea." 

South Korea's main opposition party has dismissed the White House promise as lacking sincerity.

Even as the two presidents were talking, South Korean riot police were struggling to contain tens of thousands of protesters in downtown Seoul.  Clashes erupted in the early hours of Sunday morning, after most of the demonstrators had dispersed.  Demonstrators smashed windows on police buses.

The protests, which have been otherwise mainly peaceful, have become an almost nightly fixture in downtown Seoul.  Tens of thousands of candle-waving demonstrators have essentially shut down nighttime traffic on one of the city's busiest thoroughfares for nearly a week.

Most of the protesters accuse the South Korean president of being too hasty to strike a deal to resume U.S. beef imports.  They demand he cancel the deal and re-open negotiations.

Other protesters, like Bak Ki-wan, have a more extreme goal.

He says, Lee Myung-bak is finished-- we should topple him with the force of democracy unless he voluntarily resigns.

South Korea was once the world's third largest importer of U.S. beef, but banned the imports after a U.S. animal was found to have mad cow disease in 2003.   The United Nations World Organization for Animal Health has since backed Washington's assertion that U.S. beef is safe.

Despite the political pressure, the Lee administration is very hesitant to cancel the beef deal, saying it could severely impact trade with the U.S.  South Korean media report the administration is trying to broker some kind of voluntary, private-sector ban on older beef.