China has accused Indian border forces of allegedly crossing into its territory. It described the border incursion near North Indian state of Sikkim as very serious and slammed New Delhi of violating a convention signed in 1890 between Britain and China relating to Sikkim and Tibet.The cross-border tensions rapidly escalated in recent days due to a road construction by China, which both India and Bhutan oppose. It resulted in India and China reportedly deploying thousands of troops in frontier positions. The last time the two countries engaged militarily in Sikkim was in 1967.