SEOUL, June 5 (Xinhua) -- Thousands of people on Thursday gathered in downtown Seoul to protest against the government's recent agreement with Washington to resume U.S. beef imports, including parts known to have a high risk of carrying mad cow disease, said news agency Yonhap.

    There were no immediate signs of violence, but the rally comes after a series of recent clashes between the protesters and riot police.

    The police have promised not to use any kind of excessive force against the protesters after their use of water canons and fire extinguishers to disperse crowds at recent rallies caused an even larger uproar.

    Still, there were concerns of violent clashes over the weekend, as police are expected to face tens of thousands of protesters.

    The protests began last month as peaceful candlelight vigils against the April 18 deal between Seoul and Washington, have turned into an almost daily political campaign challenging many of the major pledges by President Lee Myung-bak who took office just over 100 days ago.

    Opponents say the deal allows parts -- including bones and sections of intestines -- that pose the greatest risk of transmitting mad cow disease to be imported, and that beef from cattle over the age of 30 months exacerbates the threat.

    "We're expecting the biggest number of protesters over the next five days," Yonhap quoted a National Police Agency official by saying.

    Seoul halted U.S. beef imports in 2003 after Washington confirmed its first case of mad cow disease. It reopened the market last year but closed it again in October after U.S. exporters violated regulations on shipments of bone-in beef products.