The employment contracts of three SMRT bus drivers facing charges of instigating an illegal strike last November have been "terminated with immediate effect", said an SMRT spokesman in a statement.

The three drivers are He Jun Ling, Gao Yue Qiang and Liu Xiang Ying. A fourth driver, Wang Xianjie, faces similar charges but he is no longer employed by SMRT as his employment contract expired on Jan 14.

In a statement on Wednesday, SMRT said the four drivers did not report to work after they were released on bail on Dec 6 last year. SMRT had "actively sought to maintain contact" with them over the past six weeks, but they had, until recently, "refused direct communication with SMRT".

He, Gao and Liu were suspended and an internal disciplinary inquiry was held on Jan 17. All three drivers were absent from the inquiry proceedings.

The SMRT disciplinary board convened for the inquiry found the three drivers to have been "absent from work without prior leave or reasonable explanation for their absence" between the time of their release on bail and suspension. They also did not inform SMRT of the reasons for their absence.

"The conduct of He, Gao and Liu in this regard is in breach of their respective employment contracts, and their employment contracts have been terminated with immediate effect."