"I am ordering a speedy prosecution to keep this recidivist from doing it again, and to warn others from copycat behaviour," Gloria Arroyo said in a statement.
"This government shall not stand for prank-terrorism"
"The end does not justify the means," she said. "Despite the seemingly noble issues being raised in this bizarre drama, this government shall not stand for prank-terrorism."
Arroyo's chief aide, Edgardo Ermita, conceded that the incident, broadcast live on television worldwide, had been "really embarrassing".
In a brief speech before he freed the children and made via a public address system connected to the bus, Ducat had apologised for taking what he called "this harsh step".
"I ask the forgiveness of the people of Parola," he said, referring to the slum neighbourhood in Manila where most of the children live. "I did what I did because of my love for you."
It has since been revealed by police that grenades carried by Ducat and his accomplice had no detonators.
However, other weapons, such as an Uzi submachine gun, were real and carried live ammunition, officials said.
|Police have said Ducat is a veteran |
During the tense standoff, Ducat called a radio station and demanded free education and free housing for 145 pre-school children, including those on the bus, at the day-care centre he runs in the city's slum Tondo district.
Police have described Ducat as a veteran attention-seeker who kidnapped two priests 20 years ago.
In 1995 he climbed to the top of a monument in Manila in a stunt to demand that Chinese-Filipinos be disqualified from elections.
That has raised questions in the Philippine media as to how a man with such a record could be allowed to be in charge of a children's day-care centre.
But many in the Philippines have expressed a degree of support for Ducat's aims, even if they do not agree with his actions.
During Wednesday's siege, many onlookers chanted Ducat's name in what appeared to be support for his appeal to give the children a better future.
At Ducat's centre, mothers who had placed their children in his care expressed their support for him.
"He has been very kind to us. He put up this school. Dozens of pre-schoolers have finished here, learnt their ABCs here"
Mary Jane dela Cruz,
"He is a good person," Mary Jane dela Cruz told the AFP news agency. "I don't personally know his background, but he showed up here two years ago, and lived among us."
"He has been very kind to us. He put up this school. Dozens of pre-schoolers have finished here, learnt their ABCs here."
She said that she and other mothers would appeal against his conviction.
The drama began on what was supposed to be an annual field trip for the young children, most believed to be under five years old, to a mountain resort.
Instead, the bus ended up parked near city hall with a handwritten message stuck to the windscreen saying the children and teachers were being held hostage.
Speaking to the Associated Press from his holding cell on Thursday, Ducat said he did not regret his actions.
"No, I don't regret anything," he said. "The children's wishes were fulfilled, all 145 children can now go to school all the way up to college.
"However, I'm afraid there's word that I might be given a life sentence."
The 26 children held on the bus were taken to a hospital after their release where medical staff said all were in good health. They were expected to be discharged on Thursday.