Russians march into Czechoslovakia Prague radio announced early today that troops of the Soviet Union, Poland and east Germany started to cross the Czechoslovak border at 11 o'clock last night without the knowledge of the Czechoslovak President, the Chairman of the National Assembly, or the First Secretary of the Communist Party of Czechoslovakia. The Praesidium of the Czechoslovak Commnunist Party appealed to all people of Czechoslovalda not to resist the advancing troops and said the National Assembly and the Central Committee of the Communist Party had been called to meet to discuss the situation. Neither the Czechoslovak Army nor the People's Militia had been called out to defend the country, the broadcast said. Tanks block bridge on Austrian frontier Prague, Wednesday morning.- The broadcast came at 2 a.m. today over the direct broadcast network of Radio Prague. An announcer started to broadcast a statement about a meeting of the Czechoslovak Praesidum before the radio went dead. There was unusual activity at Prague airport, with jet fighters apparently landing. The broadcast said that the entry of Russian, Polish and east German troops into Czechoslo- vakia without permission "goes against the basic rights of states and relations between socialist countries ". All officials of the Govemment and of the Com- munist Party were told to remain in their jobs, and the population asked to remain calni The Czechoslovak Army of 14 divisions-the Russians have 140 divisions under arms-showed no sign of movement or action. The Czechoslovak Communist Party Praesidiuni had held a meeting last night. There was no indication of what it discussed, but it meets from time to time without issuing any statement. The meeting took place as Czechoslovakia's long - silent orthodox communists started an offensive in words in an attempt to win support before next month's Communist Party congress. The Cetaka news agency an- nounced yesterday that the Soviet tourist agency Putnik had can- celled plans for young people to visit Czechoslovakia. It said that 66 groups of young people from the Soviet Union were to have travelled in organized tours to Czechoslovakia but that only five groups had in fact arrived. The other journeys were cancelled without any reason being given. Vienna, Wednesday morning.- Travel to Czechoslovakia from the west has been barred since early today. the Austrian Interior Ministry said today. From mid- night last night, travel to Hungary from Austria had also been stopped. An official of the Ministry said tanks were blocking the bridge at Bratislava: He said he was told by Austrian travellers who were still allowed to pass the Czecho- slovak checkpoint that soldiers in the tanks had ordered them to go back to Austria. Soon afterwards, travel was also blocked at the checkpoint. The official said the travellers could not say if the tanks were Russian or Czech. There was information at the Interior Ministry, however, that Soviet tanks were moving from Hungary into Czechoslovakia, and that they might have taken over border guard duty. The entry ban into Hungary came into force at midnight at the main crossing point of Nickels- dorf facing the Hungarian border check point of Hegyeshalom. The closing of the Czechoslovak border was done in a-more erratic way, leading to the belief that the Czechoslovak border officials were surprised by the sudden order. The official said he had not yet received word from smaller border crossing points, about the situation there. He said there were no reports so far of any Czechoslovak refugee movement into Austria. When the Russians smashed the Hungarian uprising, more than 100,000 Hungarians streamed into Austria. Austrian Government leaders were immediately informed of the development and officials were taking a wait-and-see attitude, with no immediate measures ordered. An official of the Defence Ministry said Austrian Army leaders had been informed of the situation. The closing of the Hungarian border was apparently done to shield the movement of Soviet units which are stationed in Hungary. Mr. Dubeek, the Czechoslovak leader, shaking hands with Mr. Brezhnev, the Soviet Communist- Party leader, after the Bratislava talks earlier this month. Russians march into Czechoslovakia PEOPLE TOLD BY PRAGUE NOT TO RESIST