WARSAW, Poland (AP) _ A senior Interior Ministry official accused Solidarity activists in Poland and abroad of cooperating with the CIA and said some members of the banned trade union were being investigated for treason, Polish newspapers reported today.

Col. Zbigniew Pudysz, director of the Interior Ministry's investigative office, said a Polish exile, Jacek Knapik, had returned to Poland after 10 years carrying documents that indicated there are links between Solidarity and Western intelligence services.

''These documents show the ties of Solidarity abroad with the Temporary Coordinating Commission (Solidarity underground leadership) in Poland and ... Western intelligence services,'' said Pudysz.

He identified Knapik as the vice-president of the Union of Poles in Austria.

In Brussels, the Solidarity Coordinating Office issued a statement claiming Polish authorities were using forged documents to try to discredit the labor movement. The organization said it does not know who Knapik is.

Pudysz said the main military prosecutor's office is investigating the Brussels Solidarity office on charges of ''state treason.''

Pudysz made his remarks in an interview for Polish TV broadcast nationwide Sunday evening. A report on the interview by the official Polish news agency PAP was prominently displayed in major Polish newspapers today.

Pudysz displayed what he said were Solidarity documents and computer disks supplied by Knapik. He also read from a letter allegedly written last year by Jerzy Milewski, the head of Solidarity's Brussels office, to Bogdan Lis, the former Gdansk Solidarity underground leader.

Pudysz claimed the letter described Milewski's contacts with officials from the U.S. State Department's Eastern European section.

''He (Milewski) is received there ... because the CIA opens these doors to him,'' said Pudysz. ''It shows a strict correlation between this service and Milewski's activities.''

Meanwhile, Solidarity chief Lech Walesa, who was warned by a state prosecutor that he faces up to five years in prison if he continues his union activities, reported today to his job as an electrician at Gdansk's Lenin Shipyard.

''I returned to work and nothing happened,'' said Walesa, contacted by telephone at his Gdansk apartment. Walesa returned to work after a four-week vacation and sick leave.

The union leader, ignoring a prosecutor's warnings about his activities, is urging supporters to join a 15-minute strike on Feb. 28 to protest government plans to raise food prices.

''As of this moment we are starting a counteroffensive, so let's get ready for it in peace,'' witnesses quoted Walesa as telling more than 1,000 supporters on Sunday in Gdansk. He later confirmed the accounts.

Walesa, 41, who won the 1983 Nobel Peace Prize, was charged Saturday with inciting unrest and organizing illegal protests.The strike appeal is the first time Walesa has openly endorsed a call for work stoppages since the December 1981 military crackdown.

''Regardless of whether I am arrested or not, everyone knows what he is supposed to do on Feb. 28,'' he said. ''If the general (Polish leader Gen. Wojciech Jaruzelski) is not able to ensure order in this country then we will help him.''

In Warsaw, Western diplomats and opposition activists said the Pudysz interview and the prosecutor's decision to file charges against Walesa reflects a wide campaign to dissuade Poles from taking part the general strike.

''Maybe they (the authorities) are trying to frighten people before Feb. 28 or are launching a general campaign against the opposition,'' said a prominent Warsaw opposition activist, speaking on condition he not be identified. ''I myself am afraid.''

Walesa was summoned to the Gdansk prosecutor's office on Saturday. His lawyer, Jacek Taylor, said Walesa was told that he and the seven union activists had been charged with inciting public unrest and organizing illegal protests after a clandestine union meeting in Gdansk last week. If convicted, the eight face a maximum three-year sentence.