He was referring to the recent intrusions by Malaysian government vessels into Singapore waters off Tuas.
"This violation of Singapore's sovereignty is a serious new issue in our bilateral relations with Malaysia," he said. "We will protect and defend Singapore's territorial sovereignty."
"Singapore will not hesitate to take firm actions against intrusions and unauthorised activities in our waters," he added.
He also asked Singaporeans to stay united as one people with regard to this issue.
After Khaw's announcement of Singapore's stand on Thu, MINDEF made an announcement yesterday (7 Dec) that the SAF will conduct military exercises across Singapore next week, including live-firing exercises by the army and air force.
It said that SAF will conduct live-firing exercises in Pasir Laba (Safti) Live Firing Area from 8am on Monday to 8am the following Monday (1 week). Live ammunition and flares will be used, it added.
MINDEF also said that sea vessels and craft sailing through the Western Johor Strait during this period are to keep within the 75m Navigable Sea Lane and not to stray into the Live Firing Boundary as RSAF will also be conducting live-firing exercises around Pulau Sudong, Pulau Pawai and Pulau Senang the whole week.
RSAF will carry out air strikes around these 3 islands from Monday to Friday from 7am to 11pm, and from Saturday to Sunday from 12.01am to 11.59pm, next week. Flares will be released during night firing. It is said that the drills are meant for National Day Parade rehearsals.
MINDEF advised the public to keep clear of these three locations which lie within the live firing areas.
Furthermore, SAF will also conduct multiple military exercises in the following areas: Seletar, Marsiling, Jalan Bahar, Neo Tiew, Lim Chu Kang, Jalan Kwok Min, Tuas, Upper Jurong, Hong Kah, Ama Keng, Bedok Jetty, Kranji, Lentor, Simpang, Sembawang and Mandai. These will take place from 8am on Monday to 8am the following Monday. Blanks and thunderflashes will be used.
It advised the public not to be alarmed and to keep clear of the exercise areas.
ST reported that the MINDEF's announcement was a routine one.
"For 20 years or more, the Republic of Singapore Navy and Police Coast Guard ships have patrolled our Singapore Territorial Waters at Tuas. Out of nowhere, Malaysian Government vessels now claim these waters as theirs and have been continually intruding since November.
These are serious violations of Singapore's sovereignty. Our security forces have acted with restraint despite continuing intrusions and provocations. Singaporeans are peace-loving, but I strongly caution violators to leave Singapore territorial waters."