According to police, Mansur Mahashev personally prevented the foster parents from calling the police as Somaja (eight) and Rajana (six), were bundled into a car by two masked men on Tuesday.
He then sprinted away and has not been seen since. The girls' mother was also charged on Thursday with possible complicity in the abduction.
According to Mahashev's lawyer John Christian Elden, Mahashev, a Russian citizen, risked losing custody of the two children within weeks, after Norway's Child Welfare Services intervened following reports of violence and neglect.
Elden said that the reason for the Child Welfare Services' intervention was "parenting violence", of a level, he said, that was "allowed in their country, but illegal in Norway".
"The allegations are that the father gave a few little spanks to the children in their early childhood," Elden told NRK.
He argued that it was wrong of police to charge the man with kidnapping as officially the parents still have legal custody of the children, who are only in temporary care.
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"I have asked the police to waive the charges, simply because the Supreme Court in early 2013 said that you can not kidnap you own children," he said. "If it is true that parents have taken the children back to their home country, or out of Norway, it is not a criminal offence."
Police lawyer Irene Johnsen Dahl told NRK that the authorities did not intend to waive the charges completely, but had instead changed them from kidnapping to 'deprivation of liberty'.