WASHINGTON  The United States has blocked $30 billion in Libyan government assets since President Obama announced his executive order late Friday night imposing unilateral sanctions against Colonel Muammar el-Qaddafi and his family, the Treasury Department said Monday. It is the largest amount of foreign assets ever seized in an American sanctions action.

David Cohen, acting undersecretary for terrorism and financial intelligence, said that an unspecified number of American financial institutions this past weekend shuttered access to funds belonging to both the Libyan government  in particular its oil-heavy sovereign wealth accounts  and the Qaddafi family. The shutdowns are part of the Obama administration’s attempt to punish Colonel Qaddafi for the government’s violent crackdown against protesters in the last 10 days.

The sheer value of the assets, blocked in just three days, speaks to the vastness of the holdings acquired by Colonel Qaddafi and the oil rich country in the four decades that the Libyan autocrat has held power. “This is the largest blocking under any sanctions program ever,” Mr. Cohen said. The $30 billion is separate from Libyan government funds which are being blocked by European countries and banks under separate orders.

Administration officials have said they believe that Colonel Qaddafi and Libya, which only two years ago was restored to full diplomatic relations with the United States, have much more wealth scattered throughout Europe than in American financial institutions.