SEOUL, April 16 (Reuters) - Samsung Electronics asked a court on Thursday to block its South Korean labour unions engaging in illegal ‌activities during strike, a spokesperson said, as a wage dispute ‌threatens to disrupt operations at the world's top memory chipmaker.

Unionised workers at Samsung last month ​voted to authorise strike plans and threatened to walk out for 18 days from May 21, should they fail to agree on a wage deal with management.

The unions also plan to hold a major rally on April ‌23, ramping up pressure ⁠on Samsung during wage negotiations.

The unions labelled Smasung's legal action a "declaration of war," accusing the company of infringing on ⁠its right to strike, which is protected under the law.

Samsung said in a statement that it does not intend to impede the union's legal right ​to industrial ​action but to prevent unlawful actions ​such as the occupation of ‌production lines.

Samsung workers, frustrated by a pay gap with crosstown rival SK Hynix, are calling on Samsung to remove its performance pay cap and link bonuses to operating profit.

The company estimated it made an operating profit of 57.2 trillion won ($38.85 billion) for the January to March period, more ‌than an eightfold jump from 6.69 trillion ​won a year earlier.

Samsung's union leader told ​Reuters that a potential strike ​could affect about half the output at Samsung's giant ‌semiconductor complex in Pyeongtaek, south of ​Seoul, the capital.

A strike ​at the world's largest manufacturer of memory chips could worsen bottlenecks in global supply of semiconductors, stemming from robust demand for ​artificial intelligence data centre ‌operations that has curbed supply to industries from cars and computers ​to smartphones.

($1 = 1,472.2600 won)

(Reporting by Hyunjoo Jin; Editing by Jacqueline ​Wong, Ed Davies and Louise Heavens)