SINGAPORE (Reuters) - Indian Prime Minister Narendra Modi stressed on Friday the importance of ensuring the freedom of navigation in Asian waters for free trade, days after pledging to help develop a strategic port in Indonesia.

Modi is visiting three countries in Southeast Asia this week as part of an “Act East” policy of strengthening relations in the region amid concern over China’s rising maritime influence, in particular in the disputed South China Sea.

“We also reiterated our principal stance, as far as maritime security is concerned, our commitment to a rules-based order,” Modi said through an interpreter after holding talks with Singaporean Prime Minister Lee Hsien Loong.

“We also agreed on having an open, fair and transparent maritime trade commitment in this area,” Modi said.

On Wednesday, Modi met Indonesian President Joko Widodo and pledged to develop infrastructure and an economic zone at Sabang, on the northern tip of Sumatra island at the mouth of the Malacca Strait, one of the world’s busiest shipping lanes.

Modi stopped in Kuala Lumpur briefly on Thursday to meet newly elected Malaysian Prime Minister Mahathir Mohamad before arriving in Singapore, where he will deliver the keynote address at the annual Shangri-la Dialogue security forum.

Modi’s talks in Singapore included an agreement for greater engagement between their navies including exercises.

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“Both prime ministers further agreed to India’s proposal for continuous and institutionalized naval engagements in their shared maritime space, including the establishment of maritime exercises with like-minded regional partners,” the Singapore Defence Ministry said in a statement.

Modi this year invited the leaders of all 10 Association of South East Asian Nations (ASEAN) countries to India Republic Day parade in New Delhi, the biggest such gathering of foreign leaders at the event.

There has been growing unease about China’s activity in the South China Sea, which it claims almost in full, and which Brunei, Malaysia, the Philippines, and Vietnam claim in part.

U.S. Defense Secretary Jim Mattis said on Tuesday the United States would push back against what it sees as China’s militarization of islands in the South China Sea despite China’s condemnation of a voyage through the region on the weekend by two U.S. Navy ships.