Milos Jakes, the last head of the party, is the most senior to be charged. Others include a former prime minister, Jozef Lenart, and Karel Hoffman, the director of the Czechoslovak telecommunications network in 1968.
The charges are the most serious to be brought against former Czechoslovak leaders since the collapse of Communism in November 1989. They are also among the most extensive of those brought anywhere within the ex-Communist bloc over the past six years.
In Prague there was a mixed response to the news. Commentators on the right applauded the decision, saying thatthose who had brought misery to millions would now be brought to justice. The extreme left condemned it as a flash- back to the show-trials of the Stalinist era.
Mr Jakes, 73, described the charge of treason as "absurd nonsense", while Mr Hoffman denounced it as "utter fabrication". But Pavel Bret, the deputy director of the Office for the Investigation of Communist Crimes, said they had "helped to realise the occupation". They had also been responsible for the deaths of hundreds of Czechs and Slovaks after the invasion, he said.
The decision to send the tanks into Czechoslovakia on 21 August 1968 followed months of growing liberalisation in the country under the leadership of Alexander Dubcek. Moscow declared that it had been urged to intervene by pro-Soviet workers and agricultural labourers who wanted an alternative to the Dubcek government.
At the time of the invasion, Mr Jakes was a relatively low-ranking party official. Shortly afterwards, he rose to prominence under the leadership of Gustav Husak and initiated a purge of all those who had supported theDubcek reforms.
If Mr Jakes and his former colleagues are successfully prosecuted, they will join the small circle of former East European Communist leaders to be jailed for crimes directly relating to their activities while they were in power.
While some Czechs believe it is too late to prosecute those responsible for 1968, others welcomed the development.
"We have a moral responsibility to deal with this part of our past," said Jaroslav Veis of the Prague Centre for Independent Journalism. "What happened in 1968 is still unfinished business. If these people are punished for high treason, it will have a great symbolic value."
However, those seeking some sort of retribution will have to content themselves with a half-measure. Many of those who colluded in the 1968 invasion now live in Slovakia, which has been a separate country since 1993. They remain out of the clutches of the Czech authorities.