North Korean leader Kim Jong Un appeared to be handling state affairs as usual, South Korea’s government said Tuesday after unconfirmed rumors described him as in fragile condition after surgery.

The presidential Blue House said no unusual activity has been detected in North Korea and it had no information about the rumors regarding Kim’s health. Speculation often surfaces about North Korea’s leadership based on attendance at important state events. Kim, who is in his mid-30s, missed the celebration of the birthday of his late grandfather and state founder Kim Il Sung on April 15, the country’s most important holiday.

But he had presided over a meeting on April 11, discussing coronavirus prevention and electing his sister as an alternate member of the political bureau of the ruling Workers’ Party, the North’s official Korean Central News Agency said. State media have since reported Kim sent greetings to Syrian President Bashar Assad and Cuban President Miguel Díaz-Canel as well as “birthday spreads” to two North Korean officials and a new centenarian.

“We have no information to confirm regarding rumors about Chairman Kim Jong Un’s health issue that have been reported by some media outlets. Also, no unusual developments have been detected inside North Korea,” Blue House spokesman Kang Min-seok said in a statement.

The Blue House later said Kim was believed to be staying at an unspecified location outside of Pyongyang with some of his close confidants. It said Kim appeared to be normally engaged with state affairs and there weren’t any unusual movements or emergency reactions from the North’s ruling party, military or Cabinet.

A U.S. official said the White House was aware before the reports appeared late Monday that Kim’s health might be precarious. The official said the U.S. had information that Kim may have undergone surgery and that complications may have rendered him “incapacitated or worse.” But, the official stressed that the U.S. had nothing to confirm the surgery had taken place or that any complications had occurred.

The U.S. official, who was not authorized to discuss the matter publicly and spoke on condition of anonymity, would not elaborate on where the information came from or when it had been received. The White House and State Department had no comment.

Conservative South Korean lawmaker Yoon Sang-hyun, chairman of the National Assembly’s foreign affairs and unification committee, said he was told by unspecified non-government sources that Kim had surgery for cardiovascular problems. But an official from Seoul’s National Intelligence Service, who didn’t want to be named, citing office rules, said the spy agency couldn’t confirm whether Kim had surgery.

Kim In-chul, spokesman of South Korea’s Foreign Ministry, said Seoul and Washington are maintaining close communication but didn’t provide a direct answer when asked whether the allies exchanged any meaningful intelligence about Kim’s health.

Japanese Chief Cabinet Secretary Yoshihide Suga said his government was monitoring the situation.

A political upheaval in North Korea would be unlikely even if Kim became sidelined by health problems, according to analyst Cheong Seong-Chang at the private Sejong Institute in South Korea.

Cheong said Kim’s sister, Kim Yo Jong, is already exercising significant influence within the government and that most members of Pyongyang’s leadership share an interest with the Kim family in maintaining North Korea’s system.

Outside governments and media have a mixed record on tracking developments among North Korea’s ruling elite, made difficult by Pyongyang’s stringent control of information about them.

In 2016, South Korea media quoted intelligence officials as saying Kim Jong Un had had a former military chief executed for corruption and other charges. But months later, North Korea’s state media showed Ri Yong Gil alive and serving in new senior posts.

Kim’s absence from state media often triggers speculation. In 2014, Kim vanished from the public eye for nearly six weeks before reappearing with a cane. South Korea’s spy agency said days later that he had a cyst removed from his ankle.

Kim, believed to be 36, took power upon his father’s death in December 2011 and is the third generation of his family to rule the nuclear-armed country.

Kim met U.S. President Donald Trump three times in 2018 and 2019 and had summits with other Asian leaders as he pursued diplomacy in hopes of ending crippling economic sanctions and receiving security guarantees. But he maintained his right to a nuclear arsenal and most diplomacy has stalemated since.