Czechoslovakia lashed out at the United States Wednesday for criticizing its human-rights record and defended the actions of riot police who attacked crowds in Prague for a third straight day.

Witnesses said hundreds of police used water cannons and truncheons Tuesday to clear thousands of people from Prague's Wenceslas Square, where human-rights activists gathered Sunday and Monday to mark the 20th anniversary of the suicide of dissident student Jan Palach.It was unclear what prompted Tuesday's attack, although one witness said "busloads" of people were detained by authorities.

The Czechoslovak daily newspaper Rude Pravo defended the police action and rejected charges by Secretary of State George Shultz that the attack was a "glaring contradiction" to a human-rights agreement signed in Vienna Monday by Czechoslovakia and 34 other nations.

Czechoslovak Foreign Minister Jaromir Johanes, addressing the 35-nation Vienna Follow-up Conference on Security and Cooperation in Europe, as Shultz had done the day before, said, "Anyone in this hall who wishes to point the finger at other countries, including Czechoslovakia, should first of all look at himself."

The Rude Pravo article, carried by the official Czechoslovak news agency CTK, said the "U.S. delegation has the least right to act as an advocate of human rights."

"Shultz's speech can be justifiably regarded as an attempt to cast doubts on the principles of the (final document) of the Conference on European Security and Cooperation," the article said.

It described the demonstrations at Wenceslas Square as "provocative actions organized for the cameras of Western television corporations . . . to supply slanderers with anti-socialist ammunition."

Witnesses to Tuesday's disturbance in Wenceslas Square said it was not clear what precipitated the massive deployment of police. Earlier in the day, heavy patrols of police had approached people in the square and asked them to leave.

"There was lots of water cannon and police used the same brutal force as yesterday (Monday), although there were not so many on the square," said one witness, who added no tear gas was used Tuesday. "It was quite surprising."

"My girlfriend was just there and asked some people what happened and they said nobody started it - just police," said an activist who was not at the square.