BEIJING, April 19 -- Compatriots on both sides of the Taiwan Strait should stand on high alert against "Taiwan independence" separatist activities, said a mainland spokesperson on Thursday.

Ma Xiaoguang, spokesperson with the State Council Taiwan Affairs Office, called such activities the biggest real threat to the peace and stability across the Strait.

"No individual or element should underestimate our resolve and ability to safeguard national sovereignty and territorial integrity," he warned when responding to a question about the People's Liberation Army Air Force's recent island patrols.