3 suspects arrested in connection with assassination of Kim Jong Un's half brother Kim Jong Nam is believed to be assassinated.

 -- Three suspects have been arrested in connection with the apparent assassination of North Korean leader Kim Jong Un’s exiled half-brother, Kim Jong Nam.

The suspects – two women and a man – were picked up separately by Malaysian police Wednesday and early Thursday as investigators work to piece together details of the case, which centers in part on speculation that Kim Jong Un hired a hit squad to murder his estranged sibling.

According to the Royal Malaysia Police, a North Korean man who “sought initial medical assistance” at the customer service counter in the Kuala Lumpur International Airport on Monday died as he was being transported to the hospital. Police said the 46-year-old man was carrying North Korean travel documents bearing the name Kim Chol with a birth date of June 1970 and birthplace of Pyongyang, the capital of North Korea. The cause of death remains under investigation, police said.

The name on the travel documents, Kim Chol, is the name of another brother of Kim Jong Un, but the birth date matches the reported age of Kim Jong Nam, who is believed to be 45 or 46.

On Wednesday, Malaysian authorities investigating the death arrested a woman carrying Vietnamese travel documents at Kuala Lumpur International Airport, where Kim Jong Nam was allegedly attacked. The suspect was alone at the time of the arrest and she was identified using surveillance footage from the airport, according to a statement from the Royal Malaysia Police.

The woman’s travel documents said her name was Doan Thi Huong with a birth date of May 1998, police said. It’s unclear whether the documents were genuine.

On Thursday morning, Malaysian authorities arrested another woman believed to be involved in Kim Jong Nam's death. The suspect was alone at the time of the arrest and she was carrying an Indonesian passport bearing the name Siti Aishah with a birth date of February 1992 and birthplace of Serang, Indonesia. She was also identified using surveillance footage from the airport, according to a statement from the Royal Malaysia Police.

Malaysian authorities announced a third arrest in the case later Thursday. The Royal Malaysia Police said in a statement that a Malaysian man, identified as 26-year-old Muhammad Farid Bin Jalaluddin, was arrested to “assist in investigations.” Police believe the man is the boyfriend of the suspect carrying an Indonesian passport.

The Royal Malaysia Police said the investigation is ongoing.

Two senior Malaysian government officials, who spoke on condition of anonymity because the case involves sensitive diplomacy, told The Associated Press that the victim was Kim Jong Nam, the estranged older half-brother of North Korea’s leader who had been living overseas for years.

The Malaysian officials said Kim Jong Nam was targeted on Monday in the airport’s shopping area before he went through immigration for his flight to Macau, where he is believed to have been living in recent years. They said he told medical workers before he died that he had been attacked at the airport with a chemical spray, The Associated Press reported.

Multiple South Korean media reports, citing unidentified government sources, said two women believed to be North Korean agents killed Kim Jong Nam with some kind of poison before fleeing the scene in a taxi.

Surveillance footage that appears to be from the domestic check-in area at the Kuala Lumpur airport has surfaced this week, but has not been verified by Malaysian police. The footage shows two women approaching a man who resembles Kim Jong Nam. One woman is wearing a white t-shirt adorned with the letters “LOL.” It's unclear whether the female suspects arrested are the same women seen in the surveillance footage.

The South Korean Unification Ministry said Wednesday it recognized that the North Korean man who died in Malaysia’s capital was “certainly Kim Jong Nam.” The ministry did not offer further details on the alleged murder.

"The government is certainly judging that the murdered person is certainly Kim Jong Nam,” the ministry’s spokesman, Jeong Joon-hee, said in Korean at a press briefing in Seoul. “The Malaysian government did not specify [that the murdered man is Kim Jong Nam]. Since this case is still being investigated, we should wait for details until the Malaysian government makes an announcement [on details of the murder]. I will only say that the South Korean government will closely cooperate with the Malaysian government."

The State Department told ABC News on Tuesday that it was aware of the reports about Kim Jong Nam’s alleged assassination and referred questions to Malaysian authorities. The South Korean embassy in Washington, D.C., said it did not have independent confirmation of the reports but was monitoring media coverage.

As Kim Jong Il’s eldest son, Kim Jong Nam was initially seen as the heir apparent to the late leader of North Korea’s regime. But Kim Jong Nam was pushed out of the succession plan and his younger half-brother, Kim Jong Un, inherited their father’s power.

Kim Jong Nam reportedly fell out of favor after he was caught trying to enter Japan on a false passport in 2001. He was on his way to visit Tokyo Disneyland, he said.

ABC News’ Joohee Cho, Conor Finnegan, Benjamin Gittleson, Matt Gutman, Joshua Hoyos, Luis Martinez and Joseph Simonetti contributed to this report. The Associated Press also contributed to this report.