The anniversary of the assault on tiny Kinmen island, known as the "823 bombardment", comes as China steps up pressure on self-ruling Taiwan, which it sees as part of its territory to be reunified.

China's People's Liberation Army fired 470,000 shells at Kinmen and nearby islets in 1958, killing 618 servicemen and civilians in an attack that lasted 44 days.

Kinmen is part of Taiwan, but lies less than two miles off mainland China, at the narrowest part of the Taiwan Strait.

"When we remember the '823 bombardment' 60 years later, we will not forget the spirit of solidarity," Tsai said on her Facebook page.

"When we face diplomatic suppression we will not forget how strong our country can be when we are united," she added, saying that while Taiwanese people cherished peace they would not take national security for granted.

Tensions with Beijing have worsened under Tsai because she refuses to acknowledge that Taiwan is part of "one China".

In response, China has ramped up military drills and poached Taiwan's official diplomatic allies -- El Salvador became the third this year to switch ties from Taipei to Beijing on Tuesday.

At an anniversary ceremony held in a former army bunker and combat centre in Kinmen, Taiwan's Defence Minister Yen De-fa said today's troops in Taiwan must again make "combat preparations" in the face of what he described as a growing military threat from China.

Hundreds of soldiers, relatives and veterans, some in their 80s and 90s, gathered at a Kinmen cemetery where victims of the 1958 bombardment were buried.

Lai Jen-hsien, 83, remembered the attack.

"We were joking it was firecrackers, but then all of a sudden it was a rain of them (artillery)," said Lai, who was in the combat engineer battalion in Kinmen at the time.

He told AFP he did not think history would repeat itself on Kinmen.

"Peace is priceless. War is ruthless. We should try our best to peacefully handle the fate of people from both sides of the (Taiwan) Strait," Lai said.

China has sought to bring Taiwan back into the fold since nationalist troops fled to the island after their defeat by communist forces on the mainland in 1949.

Kinmen historically often found itself on the frontline, although now the island is a popular tourist attraction for both mainland Chinese and Taiwanese visitors.

Its most famous souvenirs are kitchen knives made from the remnants of artillery shells.