Two construction workers from China who perched themselves on top of two tower cranes at a worksite were each jailed for four weeks on Thursday.

Wu Xiaolin, 47, and Zhu Guilei, 24, admitted to criminal trespass by unlawfully remaining on two separate cranes at the Jurong Port Road site, with intent to cause alarm to the project manager of their employer Zhong Jiang (Singapore) International by their threatening behaviour.

Zhu and Wu remained on top of the cranes for about 8 1/2 hours and nine hours respectively on Dec 6 last year.

Investigation showed that Zhong Jiang had received letters from the duo on Nov 30, stating that they did not wish to work any more. According to their terms of contract, as they had worked for less than a year, they would have to reimburse the company for utilities incurred by them. Wu and Zhu were unhappy with the arrangement and informed the project manager that they would lodge a complaint with the authorities.

On Dec 6 at about 6am, Zhu climbed up the tower crane and called a fellow worker and told him where he was and that he could have his work clothes. The worker tried to persuade Zhu to come down but he refused.

Half an hour later, Wu did likewise by climbing up another crane.

Zhu, who had demanded his full salary and compensation, was arrested at about 2.45pm when he finally agreed to come down. Wu was arrested at about 3.30pm.

The court heard that numerous resources were expended as a result of their actions, causing inconvenience and delay in the construction works. They could have been jailed for up to three months and/or fined up to $1,500 each.