A Japanese court on Wednesday ordered millions of dollars compensation be paid to families of children swept out to sea by a massive 2011 tsunami.

The Sendai District Court in northern Japan ruled two local governments must pay a combined 1.43 billion yen ($13.7 million) to 29 plaintiffs -- parents of 23 children who were killed in the disaster -- according to a court spokesman.

The victims, from the public Okawa Elementary School in the city of Ishinomaki, were among a total of 74 children who perished in rising waters after being told to wait for more than 40 minutes at the school grounds with teachers, 10 of whom also died.

The plaintiffs had demanded that Ishinomaki and the larger Miyagi prefecture of which it is a part pay a total of 2.3 billion yen in compensation, arguing that their children would have survived if they had evacuated to a hill just behind the school rather than waiting.

"The teachers were able to predict the massive tsunami would reach the school," presiding judge Kenji Takamiya was quoted as saying by Jiji Press.

Public broadcaster NHK showed family members rushing towards cameras outside the court in the city of Sendai after the verdict was announced. One of them held up a banner reading, "We won: Our children's voices were heard."

"Why did my son have to die?," Kazutaka Sato, one of the parents, told NHK.

"I still ask this question although more than five years have passed since the disaster.

"I want teachers in Ishinomaki to understand how terrified my son must have been."

In response to the verdict, Ishinomaki Mayor Hiroshi Kameyama told reporters he takes the ruling "seriously", adding the city will decide as soon as possible whether or not to appeal.

In 2013, the same court ordered a kindergarten pay a combined 170 million yen in damages to parents of four children who died after being put on a bus that drove towards the incoming tsunami.

A massive undersea quake on March 11, 2011, sent a giant tsunami barrelling into Japan's northeastern coast, leaving more than 18,500 people dead or missing, and sending three reactors into meltdown at the Fukushima nuclear plant.

It was Japan's worst postwar disaster and the most serious nuclear accident since Chernobyl in 1986.