Zimbabwe today seized the passport of former prime minister Ian Smith, who sharply criticized the government of Prime Minister Robert Mugabe during a visit to the United States and Britain.

Smith told reporters a government official gave him a letter from the passport office demanding that he turn over the document. The move was ordered by Home Affairs Minister Herbert Ushewokunze, Smith said, but no reason was given.

"I'm a bit taken aback," Smith said. "I don't know what I have done."

A source close to Mugabe said several Cabinet ministers were upset by Smith's criticism of the government while he was in Washington, saying it could affect Western investment and aid.

"There is a very strong feeling . . .that Smith has to be shown that the government can get nasty with him," the source said, and "ground him" until it is clear he will "behave himself."

Smith, the last prime minister of white-ruled Rhodesia, ordered the withdrawal of a number of passports during his 15 years in office, but he has said that was because the country was fighting a war against nationalists seeking black rule.

It was not known if Mugabe ordered the removal of Smith's passport or whether Ushewokunze acted on his own as he has done in the past.

Much of the criticism of Smith has focused on an interview he had last month with The Washington Times in which he spoke of the need for economic help but added, "There is a danger of the free world falling into the trap of aiding and abetting the establishment of a one-party Marxist dictatorship" in Zimbabwe.

He also said that "there has been a rapid deterioration" in the country since Mugabe was elected in 1980.