Service on the Circle Line (CCL) and the East-West Line (EWL) was disrupted yesterday during the evening and morning peak hours respectively.
The CCL was affected by a signalling fault while the EWL was hit by a track fault, rail operator SMRT said in separate announcements.
It apologised for both delays.
SMRT announced the CCL fault on Twitter at 7.30pm. It said there was no train service from Stadium station to Dhoby Ghaut and Marina Bay stations.
In an updated message 14 minutes later, SMRT added: "Please seek alternative transport. We are working to recover service."
At 8.05pm, the operator announced that the disruption had been confined to the stretch between Dhoby Ghaut and Esplanade stations.
Normal train service eventually resumed at 8.43pm.
One commuter, Mr Lionel Kehan Tan, who responded to SMRT's tweet, said he was stuck on a train between the Esplanade and Promenade stations for about 22 minutes as a result of the disruption.
In a Facebook post later in the evening, SMRT said faulty communications equipment had caused a loss of communication between its control centre and the trains travelling between Dhoby Ghaut and Esplanade.
Earlier in the day, a track fault had slowed trains to a crawl on the East-West Line.
The fault occurred at about 5.45am near Clementi station, and affected train services between Jurong and Queenstown stations.
SMRT tweeted an alert before 7am to say that service between Jurong East - an interchange station with the North-South Line - and Queenstown would take 30 minutes longer than usual.
At around 7am, it said the fault had been cleared and service was returning to normal. But several minutes later, it repeated the first alert.
The disruption was resolved at about 8.30am.
Train services have been smooth of late, with several uneventful weeks.
But MRT faults and delays have begun to creep up, with the North-South and Downtown lines among those affected by glitches recently.