* Kim Jong Nam died on way to hospital from Kuala Lumpur airport
* U.S. government sources suspect assassinated by N.Korean agents
* S.Korea spy agency says Kim was poisoned - lawmakers
* Kim lived in Macau under Chinese protection-lawmakers citing spy agency (Adds details from S.Korean spy agency, Malaysian official, background)
By Ju-min Park and Joseph Sipalan
SEOUL/KUALA LUMPUR, Feb 15 (Reuters) - South Korea's spy agency suspects two female North Korean agents assassinated the estranged half-brother of North Korean leader Kim Jong Un in Malaysia, lawmakers in Seoul said on Wednesday, as Malaysian medical authorities sought a cause of death.
U.S. government sources also told Reuters they believed that Kim Jong Nam, who according to Malaysian police died on Monday on his way to hospital from Kuala Lumpur International Airport, had been murdered by North Korean assassins.
South Korean intelligence believed Kim Jong Nam was poisoned, lawmakers said after being briefed by the country's spy agency.
They said the spy agency told them that the young, unpredictable North Korean leader had issued a "standing order" for his half-brother's assassination, and that there had been a failed attempt in 2012.
According to the spy agency, Kim Jong Nam had been living with his second wife in the Chinese territory of Macau, under Beijing's protection, the lawmakers said. One of them said Kim Jong Nam also had a wife and son in Beijing.
Portly and gregarious, Kim Jong Nam had spoken out publicly against his family's dynastic control of the isolated state.
"If the murder of Kim Jong Nam was confirmed to be committed by the North Korean regime, that would clearly depict the brutality and inhumanity of the Kim Jong Un regime," South Korean Prime Minister Hwang Kyo-ahn, the country's acting president, told a security council meeting.
The meeting was called in response to Kim Jong Nam's mysterious death, news of which first emerged late on Tuesday.
South Korea is acutely sensitive to any sign of potential instability in North Korea, and is still technically in a state of war with its impoverished and nuclear-armed neighbour.
TICKET TO MACAU
Malaysian police said the dead man, 46, held a passport under the name Kim Chol. Kim Jong Nam was known to spend a significant amount of time outside North Korea, traveling in Macau and Hong Kong as well as mainland China, and has been caught in the past using forged travel documents.
Malaysian police official Fadzil Ahmat said on Tuesday the cause of Kim's death was not yet known, and that a post-mortem would be carried out. Kim had been planning to travel to Macau on Monday when he fell ill at KLIA's low-cost terminal, Fadzil said.