TAIPEI, Taiwan (AP) — Taiwan's top military official was among eight people killed in an air force helicopter crash in mountainous terrain outside Taipei on Thursday, the defense ministry said. Five others survived.

As chief of the general staff, Gen. Shen Yi-ming was responsible for overseeing the self-governing island's defense against China, which threatens to use military force if necessary to annex what it considers part of its territory.

The helicopter was flying from Taipei to the nearby city of Yilan for a New Year's activity when it crashed. The victims included other senior military officials and the two pilots.

The UH-60M Blackhawk with 13 people on board dropped from the radar screen 10 minutes after takeoff from Songshan air force base around 7:50 a.m., Taiwan's defense ministry said. It went down in the mountainous, heavily forested Wulai area southeast of the capital.

Shen, 63, had taken over as chief of the general staff in July after serving as commander of Taiwan’s air force, which is undergoing a substantial upgrade with the arrival of the most advanced version of the U.S. F-16V fighter.

Alexander Huang, a strategic studies professor at Tamkang University in Taiwan who had known Shen for a decade, said he had stood out as a pilot and an officer.

“He was very calm and very stable and unlike other army guys he was always smiling, so he got a specific leadership style that also made him a popular leader in the entire military,” Huang said.

It will likely be months before the cause of the crash is known, but the pilots appeared to have been highly experienced.

“Of course, reasonable people would think in the direction of mechanical failure or maintenance problem, but without proof you can’t say anything," Huang said.

A special government committee will look into the cause of the crash, a defense ministry statement said.

Taiwan's military has operated Blackhawk helicopters for decades and completed a sale for another 60 UH-Ms from the U.S. for $3.1 billion in 2010. The one that crashed was a model dedicated to search and rescue and had been delivered in 2018, according to the ministry.

The loss of Shen and other high-ranking officials will require a rapid reshuffle of positions, but should have minimal effect on Taiwan's Jan. 11 elections for president and lawmakers, said Andrew Yang, a former deputy defense minister who said Shen was highly respected throughout his career.

“I don’t think the crash will have a strong impact over the elections but certainly it will affect the armed forces because so many senior officers passed away as a result of this crash," he said.

The ruling Democratic Progressive Party said in a statement on social media that all its public campaign events from now through Saturday would be cancelled.

"The loss of pillars of our country make us feel endless sorrow," the statement read.

The party has been strongly critical of China's attempts to increase economic, military and diplomatic pressure. Incumbent President Tsai Ing-wen appears on track to win a second term over her more pro-China opponent, Han Kuo-yu of the main opposition Nationalists.