Two groups of South Moluccan terrorists hijacked a train and seized a school in the north of the Netherlands in coordinated attacks today, taking some 50 passengers and more than 100 children as hostages.

The twin attacks were similar to another abduction drama staged by South Moluccans 18 months ago and occured just two days before national elections.

Dutch Prime Minister Joop den Uyl abruptly canceled political campaigning and convened an urgent Cabinet session to discuss police strategy.

By nightfall no demands had been pressed by the terrorists, and it appeared that they were prepared for a lengthy siege.

It is believed that, as in the 1975 attacks, the terrorists want the Dutch government to pressure Indonesia into granting independence to the small Pacific island group of South Molucca, an impoverished portion of the Netherlands' vast colonial legacy that came under Jakarts's rule in the 1950s.

The dual raid began around 9 a.m., when two members of a terrorist group pulled the emergency cord to halt an express train between Assen and Groningen. Five masked gunmen rushed aboard and herded hostages into first-class compartments. Some 34 passengers, most of them elderly, were released.

Minutes later, only a few miles away in the tiny village of Boven-Smidle, seven terrorists invaded a primary school and forced 105 children and six teachers into the main classroom. Fifteen pupils who are South Moluccans were freed.

The terroitsts papered over the school's windows and fired warning shots at parents who tried to speak to them through megaphones.

Police cordoned off the areas under siege and reinforced security at key points around the country, including various embassies and Amsterdam's airport.

"This is the worst attack ever on the order of the Dutch state, because of the number of children involved," said Den Uyl.

Despite the violent intrusion on the election campaign, all party leaders supported plans to hold the national vote as scheduled Wednesday.

"The democratic process of the country must not yield to the abhorent acts of a few terrorists," he said.

In December 1975, South Moluccan captured a train near Beilen and seized the Indonesian consulate in Amsterdam. The 14 terrorists surrendered after a 15-day siege, at the cost of four lives.

They were sentenced to prison terms ranging from six to 14 years, but tensions among Moluccan youths continued to smolder.

Unlike the other immigrants from former Dutch colonies, who integrated into local society, the South Moluccans have never abandoned their fevent hope of returning to their homeland to set up an independent republic.

That long-nurtured dream arose when the Nehterlands granted independence to Indonesia in 1940 and, in gratitude for the unswerving fealty of Moluccan loyalists, promised the Moluccan people self-determination.

An independent Republic of South Molucca was proclaimed April 27, 1950, but Indonesia, later forcibly incorporated the poverty-stricken territory.

Out of strict adherence to religious virtues and fidelity to the Dutch Throne, older South Moluccans have repudiated the violent tactics adopted by their offspring, most of whom have never seen their homeland.

Raised in the isolated northern region of the Netherlands, young South Moluccans have repelled state efforts to assimilate them into the mainstream of Dutch society. Officials pleas to drop the hope of repatriation have gone unheeded.

In the late 1960s, South Moluccan gangs began forming guerilla squads and accumulated small arsenals of pistols, knives and submachine guns. Police stepped up surveillance but refrained from raids, wary of provoking outcries of harassment.