Poland's military authorities reinstated tough security measures in several Polish cities today as fresh disorders were reported in the northwestern port city of Szczecin, one of the main centers of labor unrest in August 1980 that led to the birth of the now-suspended Solidarity trade union.

In a special statement to the Sejm, or National Assembly, Interior Minister Czeslaw Kiszczak revealed that Monday's protests against martial law were even wider than originally believed and that 1,372 persons had been arrested. He said that order had been restored in most of the country, and he accused the West of instigating the disturbances.

Amid gasps from the legislators, Gen. Kiszczak named nine Polish cities that had been scenes of serious street incidents on May 3--the anniversary of the granting of Poland's first liberal constitution in 1791. He said protests on a lesser scale had taken place in several other towns.

The interior minister's statement came after a day of crisis meetings in Warsaw as government and party leaders met with the martial-law chief, Gen. Wojciech Jaruzelski, to decide how to respond to the worst outbreak of street rioting since last December's military crackdown. The scale of the protests appeared to take the authorities by surprise--despite massive attendance at peaceful pro-Solidarity gatherings on May Day.

Kiszczak told the Sejm that provincial government bodies had been authorized to reimpose certain martial-law regulations relaxed during the past few months. He insisted, however, that the government would not be deflected from its declared intention to undertake major political and economic reforms.

The night curfew, relaxed only last Sunday, has been reimposed in several cities including Warsaw and the Baltic port of Gdansk, where Solidarity had its headquarters. An announcement on the evening television news bulletin said that the curfew would last from midnight to 5 a.m. for adults and from 9 p.m. for children and teen-agers.

The television announcer added that student clubs would be closed, as would discotheques and places of mass entertainment such as theaters and cinemas. In Warsaw, telephones remained cut for a second day and the use of private motor vehicles was reported to have been banned in some towns.

The television news bulletin carried film reports of the demonstrations, attempting to emphasize police action against vandalism.

Giving details of injuries on the police side, Kiszczak said 72 members of the security forces had been injured and 10 were still hospitalized. Half the injuries occurred in Warsaw, which was the scene of the most serious disturbances.

The minister said it was still impossible to give an exact figure for the number of demonstrators injured. People who witnessed the street fighting believed that the figure was likely to be much higher than that for the police. Apart from makeshift barricades, the protesters were unarmed while the security forces used water cannons, tear gas, and plastic shields.

Kiszczak said that the disturbances had been organized by "enemies of socialism" acting in conspiracy on the inspiration of reactionary forces in the West. He gave little evidence to support his charge of Western involvement, other than accusing the Munich-based Radio Free Europe of broadcasting instructions to the demonstrators.

"The imperialist forces would like to undermine socialism in our country in order to split the entire socialist community," Kiszczak said, repeating what has become almost a standard formula here.

Kiszczak said that the West, by instigating unrest in Poland, was attempting to conceal its own difficulties including what he described as "the shameful colonial conflict over the Malvinas," or the Falkland Islands.

He said that the other main centers of unrest, in addition to Warsaw, had been Gdansk, Szczecin, Elblag, Koszalin, Lublin, Torun, Krakow and Gliwice. Solidarity supporters, he said, had looted shops, burned red communist flags, attacked police installations and other public buildings.

According to eyewitness accounts from Gdansk, the street fighting there was even more bitter than in Warsaw--at one point the demonstrators reportedly marched on the police headquarters. A smaller building used as a police storehouse was said to have been burned down.

Despite the official allegations of looting, the impression of observers in Warsaw was that most of the clashes took place when riot police charged groups of demonstrators--although later, smaller groups of youths roamed the city and broke some windows.

Kiszczak and other Polish officials said the majority of the demonstrators had been under the age of 20. Of the 271 persons arrested in Warsaw he said 47 were secondary-school students and 54 were university students.

The figures implied that, despite official claims to the contrary, a sizable proportion of the demonstrators were workers and older people.

Kiszczak said all the demonstrations had taken place following a similar scenario--with protesters gathering in front of churches in advance of special commemorative services. This, he said, was proof of an organized conspiracy that he described as "the May offensive against the Polish socialist state."

"Public order was, however, restored--and will be whenever anybody tries to provoke street disturbances or other excesses," he insisted. He said the result of such riots was to delay the relaxation of martial law.

Despite his warnings of retribution for those found guilty of organizing illegal demonstrations, Kiszczak's remarks were seen here as relatively restrained. He specifically exempted the powerful Roman Catholic Church from responsibility for the disturbances, which he said were "against the interests of the church."