India's foreign ministry said on Wednesday that it was concerned about a new law passed by China last week to strengthen border protection amid a protracted military standoff between the two Asian giants along a contested Himalayan frontier.

On Saturday, China passed a dedicated law specifying how it governs and guards its 22,000-km (14,000-mile) land border shared with 14 neighboring countries, including Russia, nuclear-capable North Korea, and India.

"China's unilateral decision to bring about a legislation which can have implication on our existing bilateral arrangements on border management as well as on the boundary question is of concern to us," foreign ministry spokesman Arindam Bagchi said in a statement.

The 3,500-km-long border between India and China remains undemarcated, and the nuclear-armed neighbours have overlapping claims to large areas of territory along the frontier. The two countries fought a border war in 1962.

Thousands of Indian and Chinese troops also remain amassed along a remote Himalayan border in the Ladakh region, where the two militaries have been locked in a high-altitude face-off since last year, despite more than a dozen rounds of talks.

"We also expect that China will avoid undertaking action under the pretext of this law which could unilaterally alter the situation in the India-China border areas," Bagchi said.