Will bus service 666 travel on the highway to hell? That quip was among online responses to the new service, which sports a number linked to the devil in Christianity.

The new service runs from Punggol to the city and starts operating next Monday. It was among five new City Direct Services announced on Monday by the Land Transport Authority (LTA).

The others are service 667, serving Clementi and Dover; 668, serving Ang Mo Kio; 669, serving Bedok; and 670, serving Yishun.

The LTA's Facebook post introducing service 666 drew about 90 comments as of yesterday evening.

Most were amused and joked about the association with Satan. Facebook user Sivaraj Pragasm quipped: "(I) always suspected Satan was living in Punggol."

But others were serious and concerned it could be insensitive to Christians. "Couldn't you guys have chosen another number? This is so insensitive," commented Mr James Poon on LTA's Facebook post.

"Singapore being a multiracial and multireligious society, our government services should put more thought into such details," Mr Poon, a 30-year-old Christian who is self-employed, told The Straits Times. LTA declined to comment.

City Direct Services connect the heartland with the Central Business District and run on weekdays during morning and evening peak periods, excluding public holidays.