China has invested millions of dollars in recent years building seaports and highways in countries stretching from the Maldives to Sri Lanka that lie on vital shipping lanes through which much of its energy supplies and trade passes. "So, the Indian ocean region is at the top of our policy priorities," he said in a speech.
India, alarmed at the prospect of China building a network of friendly ports in a "String of Pearls" across the Indian Ocean, has stepped up its diplomacy, offering a range of civil and military assistance.
On Wednesday, as Modi toured Mauritius, officials signed an agreement to upgrade sea and air links on the remote Agalega islands, offering India a foothold in an area hundreds of miles from its coast.
The two sides have been discussing North and South Agalega islands for years but there have been reservations in the about opening up the area to foreign involvement.
India's foreign ministry said in a statement the agreement "provides for setting up and upgradation of infrastructure for improving air and sea connectivity ... which will go a long way in ameliorating the conditions of the inhabitants of this remote island."
The new facilities would also "enhance the capabilities of the Mauritian Defence Forces in safeguarding their interests", suggesting there would be a military spin-off to the development.
The North Agalega island has a rough air strip which would likely be upgraded under the agreement, a former Indian navy pilot said.
China has also been strengthening political relations with island nations with President Xi Jinping visiting Maldives and Sri Lanka last year where Chinese state firms have won contracts to build airports and seaports.
Modi also announced an agreement with Seychelles to develop infrastructure on Assumption island.
India has been helping Seychelles with ocean mapping to protect its exclusive economic zone and has given aircraft and launched a radar project. But it had not been directly involved in infrastructure.
Modi said 90 percent of India's trade and oil imports moved by sea and as its economy became more globally integrated it would become more dependent on the ocean.
China has considered Seychelles as a resupply port for its ships taking part in anti-piracy operations.
Modi is due in Sri Lanka on Friday, the final leg of his Indian Ocean tour.
China has invested millions of dollars in recent years building seaports and highways in countries stretching from the Maldives to Sri Lanka that lie on vital shipping lanes through which much of its energy supplies and trade passes.
"So, the Indian ocean region is at the top of our policy priorities," he said in a speech.