“The two female suspects knew that the substance they had were toxic,” he said, undercutting recent reports that the women had thought they were carrying out a prank. “We don’t know what kind of chemical was used.”

Mr. Khalid said that four North Koreans suspected of being involved in the attack were believed to have fled to their homeland. Three others — the embassy official, identified as Hyon Kwang Song, the second secretary at the embassy; an employee of the North Korean airline, Air Koryo; and a third person — were still believed to be in Malaysia.

“They’re not in custody,” he said of the three. “They’ve been called in for assistance.”

“We hope that the Korean Embassy will cooperate with us, allow us to interview them and interview them quickly,” he said. “If not, we will compel them to come to us.”

The embassy had no immediate response, although it later issued a statement demanding the release of the two women accused of the attack and a North Korean citizen being held in the case. The statement, which called the women innocent, said that they could not have applied poison with their hands, because they would themselves have died.

Malaysia’s demand to question the diplomat is sure to further inflame Malaysia’s relations with the North. North Korea has refused to even acknowledge that the man killed was Kim Jong-nam and has accused Malaysia of carrying out a politically motivated investigation to placate South Korea and the United States.