Hoffmann is the only senior official jailed over invasion

Karel Hoffmann, 80, ordered a halt to Czech media broadcasts on the eve of the Soviet invasion, blocking the Prague government's condemnation of it.

He was found guilty last year of abuse of power, becoming the first senior official convicted over the invasion.

An appeal failed but Czech President Vaclav Klaus is considering a pardon.

The president told Czech radio that it seemed strange to punish someone for violating the telecommunications law while leaving those who ordered the invasion at liberty.

Hoffmann told a news conference before heading for prison that he was ready to serve his sentence, according to Czech TV1.

"I was a communist, I am a communist and I will be for the rest of my life," he said.

Hoffmann's actions in 1968 meant the public were unaware that the reformist Communist Party leadership in Prague had denounced the Soviet military action.

The channels had already been running reports about the brutality of Warsaw Pact troops.

Treason

During his trial, Hoffmann said the guilty verdict against him did not "reflect reality".

His lawyer called it an "unfortunate political trial".

Hoffmann was originally accused of treason for colluding with a foreign power, but he was cleared of the offence after no evidence was found.

Two other former top communists, former party leader Milos Jakes and ex-prime minister Jozef Lenart were also cleared of treason over the invasion.

No other prosecutions over the Prague Spring are expected.

The then-Communist Party leader Alexander Dubcek had introduced free speech and freedom of assembly in an attempt to show communism with a human face.