The mobile service disruption affecting voice calls and text messaging for M1 customers on Tuesday morning follows several mobile outages that the three major telcos here have experienced in the past few years.

Here is a timeline of some of these incidents:

Dec 17, 2013: Some SingTel mobile customers had intermittent access to text messaging services for several hours in the late morning and early afternoon.

Dec 2, 2013: Many M1 mobile subscribers were not able to connect to the Internet for several hours in the morning. This happened after a scheduled upgrade of the network the night before.

Oct 16, 2013: M1's 3G mobile services were disrupted for about three hours in the western and north-western parts of Singapore, after an upgrading of the telco's radio network controller.

Jan 15 to 18, 2013: M1's mobile services were down for up to 71 hours, affecting 250,000 users. The telco's 3G services were down in south-western Singapore, while 2G services were out in the north-west.

The outage, said to be the worst ever experienced by a telco here, happened when one of M1's vendors was upgrading transmission equipment at its network headquarters in International Business Park.

M1 was fined a record $1.5 million by the Infocomm Development Authority of Singapore.

Jan 3 to 4, 2012: Some SingTel customers had trouble using 3G mobile services - such as data voice and text messaging - for more than four hours in the northern and western parts of Singapore on Jan 3, 2012. In a second incident the next day, some users in the west of the island were not able to access data services for over three hours on the telco's 3G network.

Oct 21, 2011: Some StarHub customers could not make or receive voices calls for over three hours, although text messaging and data services were not affected. Power failure was said to be the cause of the disruption.

Sept 6 to 7, 2011: SingTel's mobile network was disrupted for over 22 hours. Voice, text messaging and data services were intermittent or unavailable. Several areas in the central region of Singapore were hit, including City Hall, Orchard and Shenton Way. The outage was due to a software glitch. SingTel was fined $400,000, the second highest fine ever to be meted out to a telco.

July 29, 2011: M1's 3G messaging service went down in the morning for several hours. Some users were unable to send text messages, while others were spammed with around 20 copies of a single message. Users in the south-west region of Singapore were affected.

May 18, 2011: M1's cellular networks went down for 12 hours, disrupting voice, messaging and data services for its mobile subscribers.