India is speeding up a navy modernization program and leaning on its neighbors to curb Chinese submarine activity in the Indian Ocean, as nations in the region become increasingly jittery over Beijing's growing undersea prowess.

Just months after a standoff along the disputed border dividing India and China in the Himalayas, Chinese submarines have shown up in Sri Lanka, the island nation off India's southern coast. China has also strengthened ties with the Maldives, the Indian Ocean archipelago.

China's moves reflect its determination to beef up its presence in the Indian Ocean, through which four-fifths of its oil imports pass, and coincides with escalating tension in the disputed South China Sea, where Beijing's naval superiority has rattled its neighbors.