Taipei (CNN) Taiwan has elected its first female president in a landmark election that could unsettle relations with Beijing.

Tsai Ing-wen, leader of the opposition Democratic Progressive Party (DPP), won the presidency with 56.1% of the vote, the official Central News Agency said, after eight years under the government of the pro-China Kuomintang (KMT) or Nationalist Party.

Eric Chu, the Nationalist Party candidate in Taiwan's presidential election conceded defeat late Saturday and congratulated rival Tsai Ing-wen on her victory, the agency added.

Her supporters filled streets, waving party banners and cheering to victory announcements made from a stage.

The election also marked the first time the KMT has lost control of the island's legislature. The DPP took 68 of the 113 seats in Taiwan's parliament compared to the KMT's 35.

At a post-election news conference, Tsai underscored Taiwan's commitment to democracy, calling it a value "deeply engrained in the Taiwanese people."

"Our democratic way of life is forever the resolve of Taiwan's 23 million people," she said.

But later in her speech, she also acknowledged the tenuous relationship with Beijing, saying both sides "have a responsibility to do their utmost to find mutually acceptable ways to interact ... and ensure no provocation and no surprises."

"Only through strength, can we gain more respect and protect our people & way of life." - Tsai Ing-wen to @CNNi #Taiwan2016 #TaiwanElection — Kristie Lu Stout CNN (@klustout) January 16, 2016

'Grave challenges'

Tsai's DPP has traditionally leaned in favor of independence for the island from mainland China.

That could anger Beijing, which views Taiwan as an integral part of its territory that is to be taken by force if necessary. Beijing has missiles pointed at the island.

"I voted for DPP, because it's very critical time for the Taiwan people. We have our own democracy systems, we will not be influenced by China," said Tsai Cheng-an, a 55-year-old Taipei professor.

At a Taipei polling station. Some voters tell me they are here to assert their Taiwanese identity. #TaiwanElection pic.twitter.com/Yi8Lh1vjM6 — Kristie Lu Stout CNN (@klustout) January 16, 2016

The KMT forged closer ties with China under President Ma Ying-jeou. The new president will take over from Ma, who will step down on May 20 after serving two four-year terms.

China and Taiwan -- officially the People's Republic of China and the Republic of China -- separated in 1949 following the Communist victory on the mainland in the civil war.

Photos: Taiwan goes to the polls Democratic Progressive Party candidate Tsai Ing-wen raises her hands as she declares victory in the presidential election on Saturday, January 16 in Taipei. Hide Caption 1 of 11 Photos: Taiwan goes to the polls Supporters of Tsai Ing-wen cheer at the campaign headquarters as early polling numbers arrive in her favor. Tsai, a soft-spoken U.S.-educated lawyer, is viewed as a pragmatic leader. Hide Caption 2 of 11 Photos: Taiwan goes to the polls Taiwan's ruling Nationalist Party candidate Eric Chu delivers a speech as he concedes in the presidential election. Hide Caption 3 of 11 Photos: Taiwan goes to the polls A supporter cries as Chu concedes defeat. Hide Caption 4 of 11 Photos: Taiwan goes to the polls A supporter of Taiwan's Democratic Progressive Party (DPP) holds up a placard of K-pop artist Chou Tzu-yu, a member of the South Korean all-girl band TWICE and who was forced to apologize after waving the Taiwan flag. The apology stirred angry debate. Hide Caption 5 of 11 Photos: Taiwan goes to the polls A police officer patrols a polling station as local residents line up at the Xindian district in Taipei. Hide Caption 6 of 11 Photos: Taiwan goes to the polls Tsai Ing-wen talks to journalists after casting her ballot at a polling station. She will have her work cut out balancing the interests of China, which is the island's biggest trading partner, the United States, its key ally, and the diverse demands of the island's 23 million residents.

Hide Caption 7 of 11 Photos: Taiwan goes to the polls A supporter of Chu chants slogans during a rally in Taipei on Friday, January 15. Hide Caption 8 of 11 Photos: Taiwan goes to the polls Supporters of DPP presidential candidate Tsai Ing-wen cheer at a rally on January 15. Hide Caption 9 of 11 Photos: Taiwan goes to the polls Supporters cheer while Chu parades through the streets during a rally on January 15. Hide Caption 10 of 11 Photos: Taiwan goes to the polls Chu receives a radish, meaning good luck in Taiwanese, from supporters as he campaigns in northern Taiwan on Wednesday, January 13. Hide Caption 11 of 11

The two sides have been governed separately since, though a shared cultural and linguistic heritage mostly endures -- with Mandarin spoken as the official language in both places.

The sides have agreed since 1992 on a "one China" policy, in which both governments claim sovereignty over mainland China and Taiwan -- but crucially neither recognizes the other's legitimacy.

"I voted for KMT because they are less likely to provoke cross-strait troubles. They want peace. That's why I chose them. We've lived through war, and it was not easy," said Chen, 83, a military veteran who declined to give his full name.

Taiwan's freewheeling democracy stands in sharp contrast to China's one-party state, and a cast of colorful candidates are contesting seats -- they include an ex-convict, an alleged spy and the front man of Asia's biggest death metal band.

Pop star's apology stirs anger

The strained relationship was highlighted over the weekend when teenage pop star Chou Tzu-yu made an apology for holding a Republic of China flag on South Korean TV, setting off a national debate.

From Taiwan, she is part of the South Korean pop act Twice. She appears in the video reading her apology off a sheet of paper, leading many to speculate that her Korean management company JYP Entertainment had coerced her to appease mainland Chinese fans, who represent a lucrative market.

There is only "one China", Chou said, and she will be taking a break from all China appearances to reflect on her actions.

The video even garnered a mention from Tsai in her victory speech, saying it "has shaken Taiwanese society."

"This particular incident will serve as a constant reminder to me about the importance of our country's strength and unity to those outside our borders. This will be one of the most important responsibilities for me as the next president of the Republic of China," Tsai said.

Balancing act

Tsai, a soft-spoken U.S.-educated lawyer, is viewed as a pragmatic leader but will have her work cut out balancing the interests of China, which is the island's biggest trading partner, the United States, its key ally, and the diverse demands of the island's 23 million residents.

In particular, a younger generation fears a future under the influence of Beijing and doesn't want Taiwan to become another Chinese territory.

"Taiwanese people are very peaceful. We want a peaceful relationship with mainland China, but that shouldn't mean we have to sacrifice our way of life and our democracy," said Huang Kuo-chang, leader of the New Power Party, one of a number of smaller opposition parties.

His party emerged from 2014's "Sunflower Movement," when scores of student protesters stormed and occupied Taiwan's Legislature and Cabinet building to object to a trade pact that symbolized Taiwan's deepening relations with mainland China.

The economy is a particular concern for many young people, with unemployment standing at 12% among 20- to 24-year-olds -- three times the overall jobless rate, according to official statistics.