More than 200,000 workers on strike in Poland's industrial heartland of Sileasia reached a settlement with the government tonight and agreed to return to work.

Strike leaders announced the agreement after the late-night talks with Deputy Premier Aleksand Kopec, Reuter reported from the strike headquarters at Jastrzebie near Katowice. The leaders said striking coal miners and other workers would return to their jobs Thursday.

Details of the agreement were not immediately available, but were likely to resemble the one reached Sunday between the government workers on Poland's Baltic Coast. That agreement opened the way for the formation of independent trade unions.

Meanwhile, Gdansk strike leader Lech Walesa was quoted as appealing for support from Norweigian trade unions and Poles living in other countries, the Manchester Guardian reported from Oslo. In an interview with the Norweigian newspaper Dagbladet, Walesa said: "I will in all earnestness ask the Norweigian trade movement for economic and moral assistance. We start from scratch to build new trade unions in Poland. We need all the help we can get."

[He also said he hoped Poles' living abroad "will aid their brothers and sisters here to build a new society."]

By the time the settlement in Silesia was reached tonight, the strike had spread to at least 20 mines and several steel mills in southern Poland. It was the first time that the miners, traditionally loyal to the communist leadership and particularly to Communist Party chief Edward Gierek, had joined in a strike movement.

Mine safety was an important issue in the Silesian labor disputes. The number of mines on strike nearly doubled following an underground accident Monday at the Halemba mine near Katowice in which eight miners were killed and 18 were wounded.

The accident was the latest in a series of serious mine disasters in southern Poland that have caused the deaths of about 60 miners in the last year. This time, the miners were crushed by loaded coal vans that went out of control in a narrow underground passage. But many miners blame declining safety standards on a new shift system introduced last year to maintain a continuous 24-hour operation.

Critics of the new system claim that proper maintenance and repair of the mines have been sacrificed for the sake of increased production.

Meanwhile in Warsaw, senior Polish officials attempted to dampen Western press speculation of a serious rift in relations with Moscow as a result of the decision to set up independent trade unions. It was pointed out that many of the criticisms of the strikers that appeared in Soviet commentaries were extracts from earlier articles in Polish newspapers.

One official, who declined to be named, said he believed that Poland would remain safe from Soviet intervention as long as the Communist Party remained a disciplined organization with full control over the government aparatus. Western diplomats said they agreed with this analysis.

So far there has been no internal restructuring of the Polish Communist Party comparable to that which occurred in Czechoslovakia in 1968 before the Soviet invasion. In addition, while party propaganda has now become a good deal more sophisticated, censorship has not been abolished entirely.

But the press has certainly become more interesting. Today people lined up 100 deep outside kiosls throughout Poland to buy newspapers with the full communique of the agreements reached with strikers in Gdansk and Szczecin.

"It's like a new constitutiion," commented one Pole after reading the detailed agreement, which covers points ranging from the release of political prisoners to the broadcasting of Sunday mass on state radio.

The document goes into considerable detail about how the new trade union will function and gives a legal basis to their existence. In Gdansk, workers were reported to be lining up to join the new uniion, which now has a headquarters on the outskirts of the city.

Meanwhile in Katowice, police detained one of the founders of the free trade union movement in Poland, Kazimierz Switon. But, like dissidents in Warsaw who were freed after two weeks in detention, it is expected that he will be released now that the strike in Silesia is settled.

Switon has been in almost constant trouble with the police since founding the Organizing Committee for Free Trade Unions in Upper Silesia in February 1978. He has been detained for brief periods about 20 times and received a two-month jail term for allegedly disturbing the peace.

In Warsaw, dissidents belonging to the Workers's Defense Committee celebrated their release Monday by donning T-shirts with the word "Solidarnosc" emblazoned across the chest.

The polish word for solidarity, it was the name given to the strike newspaper that circulataed in Gdansk.

The Manchester Guardian provided this account of Lech, Walesa's interview with Dagbladet from Oslo:

Walesa, the hero of the Polish strikes, told Dagbladet that he would like detailed information on the rules and organization of the Norwegian trade union movement. "We have to learn from other countries," he said, "we are starting from point zero. We have no money either, and we need it badly. Maybe someone in Norway will lend us the money."

Walesa said he would like to see a future Poland in which "everybody can feel that they are owners of their own country. It has to be a smiling, singing and happy Poland. To make this we need assistance from outside. I hope that all the Poles living in foreign countries will aid their brothers and sisters here to build a new society."

According to Dagbladet, the day after the historic deal between the Polish government and the strike committee, the trade unionists started to organize a new trade union movement. They are going to have their headquarters in a worn-down, five-room flat in Gdansk. Ten chairs with spindlebacks, a small table and a stove are the only pieces of furniture in the new offices.

"We have won the first round, now starts the second one, and that will be much tougher. I believe in total victory but we have not won yet. The most important thing is to get the new trade union movement organized," Walesa told the Norweigian interviewer.

Asked which point in the agreement he was must satisfied with, Walesa replied that he was satisfied with all the points. He was also asked what he Thought about the strong attack in the Soviet paper Pravda. Walesa replied that he had no time to read newspapers, but added, "What the Russians might think or feel is of no interest to me. Besides, it is not correct what they are writing."

Walesa was also asked if the strike committee is attracted to the socialist system of Poland. He replied that it only represents a trade union. "We are only struggling to establish a trade union movement, nothing more."

Walesa lived with the other strikers in the Lenin Shipyard for 17 days while the strike was on. His wifde and their six children were at home. "The family had to come second. But my wife said in a ceremony that she loves me until death and will not leave me. That I truust," he said.