Former Czechoslovak Communist Party leader Alexander Dubcek is being prevented from receiving visitors by police guards at his home in Bratislava, dissident sources said in Prague yesterday.

Milan Hubel, a colleague of Dubcek's in the liberal party leadership of the late 1960s, tried to visit Dubcek last Friday but was taken into custody and quesitoned for two hours by police, the sources said. He was told not to come back to Bratislava "in his own interest."

Friends of Dubcek said he had been "deeply dismayed" by allegations in an Austrian Communist newspaper that he disapproved of a manifesto drawn up by Czechoslovak liberals critical of the government's civilrights policy.

Dubcek is said to be suffering from a severe nervous breakdown.

Meanwhile, Premier Lubomir Strougal of Czechoslovakia has postponed an official visit to Vienna following criticism by Austrian Chancellor Bruno Kreisky of the Prague government's treatment of th signers of the civil-rights manifesto.

The United States protestd to Czechoslovakia about the detention of New York Times correspondent Paul Hofmann fo several hours over the weekend.

In Moscow, security police briefly detained Valentin Turchin, chairman of the Moscow branch of the human-rights organization. Amnesty International. Turchin told Western correcspondents that the police warned him he could face prosecution for anti-Soviet agitation.

Lyudmila Alexeyeva, a member of another group esatblished to monitor Soviet observance of the 1975 Helsinki declaration on rights, said that she had been granted permission to emigrate.