The notice was posted on the regional government website.
It follows a series of deadly protests in Sichuan province in January and the self-immolations of 19 ethnic Tibetans in the past year in apparent protest against Chinese rule.
Tibet celebrates its new year on 22 February.
The anniversary of deadly 2008 riots in Lhasa falls shortly afterwards, on 14 March.
‘Extreme importance’
Citing the government notice, the Tibet Daily newspaper said that officials were warned that they “must put all their efforts into maintaining a stable, unified social situation in our region”.
They were also urged to “have a clear head and fully recognise the extreme importance and urgency of the job of maintaining stability”.
Since March 2011, at least 19 Tibetans have set themselves on fire in apparent protest against Beijing’s rule. The most recent three cases happened on Friday in Seda county in Sichuan province, activists said.
Last month, three violent protests were reported in the same province. One protester was killed on 23 January in a confrontation with security forces in Draggo county, known as Luhuo in Chinese.