WARSAW, Poland (AP) _ Military leaders met in emergency session and troops moved across the southern region of Silesia on Saturday after workers at four more coal mines joined nationwide strikes to demand legalization of Solidarity.

Poland's leader, Gen. Wojciech Jaruzelski, and the national Defense Committee reached ''appropriate decisions ... in connection with the present threats,'' the state-run news agency PAP said.

The brief dispatch gave no hint about what the government planned to do about the strongest challenge to communist authorities since Solidarity, the independent union federation, was crushed in 1981.

Opposition activists said police and army were on the move in Silesia, where the 10 coal mine strikes were centered.

Unusual police movements also were reported in Krakow and Nowa Huta, the scene of a cripping steel strike last spring.

''There are helicopters flying over Jastrzebie and many army units near. Police are also erecting roadblocks at the towns' outskirts, just like during martial law,'' said Adam Slomka, a leader of the rightist opposition group Confederation for Independent Poland, in Katowice.

''We want to appeal to miners to be on the alert, put on all possible lights and make sure they will not take them by surprise.''

An Associated Press reporter saw long police convoys on the 36-mile route between the Silesia city of Jastrzebie and the provincial capital of Katowice.

''There are many army-and-police patrols, as if they suddenly ran short of police,'' Lech Bosiak, a Jastrzebie resident, said late Saturday. ''Most of the patrols are two soldiers and two police.''

A government spokesman, asked Saturday if he could rule out police intervention in the strikes, said only, ''It's 8 o'clock, and we'll have nothing more for you tonight.''

PAP carried a dispatch accusing strikers of forcibly keeping some miners locked in at the strike-bound mines and of having ''crowbars and other such objects for alleged defense action.''

Solidarity, meanwhile, observed its eighth anniversary this week. The movement was suppressed with the imposition of martial law in 1981 and outlawed in 1982.

The government rejected the demand to legalize it and said the strikes harmed every Pole.

About 40,000 workers were participating in the coal strikes, which were costing an estimated $1.3 million in lost coal production daily. Production was stopped, but it was impossible to determine what percentage of mine employees actively supported the strikes.

Spirits were high among 2,000 cargo workers occupying the docks of Poland's second-busiest port in Szczecin since Wednesday. Bus and most tram drivers there went on strike Thursday and Friday, crippling public transport.

The four mines that joined the walkouts Saturday were the 3,000-worker Krupinski mine in Suszec, the 3,500-worker ZMP mine in Zory, and the First of May and Borynia mines in Jastrzebie.

Authorities confirmed 10 coal mine strikes in the vital coal-producing region of Silesia, concentrated around Jastrzebie, a city of 100,000 people near the Czechoslovak border. Also, Solidarity activists said two more mines were on strike, but the claim was disputed by mine officials.

Solidarity activists from the Nowa Huta steel mill outside Krakow issued a statement Saturday announcing ''strike readiness.'' Workers said they would call a strike if police intervened against strikes elsewhere. A similar warning came from activists of the Ursus tractor plant outside Warsaw.

On Friday, national Solidarity leader Lech Walesa threatened a strike Monday at the Lenin Shipyard in Gdansk unless Solidarity was recognized.

A 1980 strike by the shipyard workers eight years ago gave birth to Solidarity, the East bloc's first independent trade union. Solidarity had a 15-month legal existence and signed up 10 million members before being suppressed.

Poland's Council of Ministers said in a statement Friday that legalizing Solidarity was an ''unrealizable demand,'' but workers said they disagreed.

''We will not back down from our demands that Solidarity be legalized,'' said Andrzej Milczanowski, a Szczecin docks strike leader. ''The authorities must realize if they want improvement, they must restore Solidarity.''

''I can't predict how or when it will end,'' said Edward Radziewicz, chairman of the Interfactory Strike Committee in Szczecin. ''We may win or we may be removed by force, but we cannot back up even one step, because there is only water behind us.''

The labor unrest began Tuesday at the July Manifesto Mine in Jastrzebie, one of Poland's most modern mines producing high-grade coal for export.

State-run radio and television devoted heavy coverage to the labor unrest, including reporting the demands for legalizing Solidarity. The reports emphasized the mounting cost of the strike.

The week's strikes surpassed the number of work stoppages in April and May, which until then were the worst labor unrest in the country since the 1981 martial-law crackdown.

Coal production is crucial to Poland's economy and a major source of hard currency to service its $39 billion debt to Western creditors. Poland is the world's fourth-largest coal exporter and its mining operations are essential to its steel, power and shipbuilding industries.