India and Vietnam on Thursday firmed up a new action plan to expand their strategic ties, with Prime Minister Narendra Modi asserting that both sides will work towards a free and rules-based Indo-Pacific and that New Delhi supports development and not "expansionism".

After his wide-ranging talks with Vietnamese Prime Minister Pham Minh Chinh, Modi said the agreed USD 300 million credit line for Vietnam will strengthen the Southeast Asian nation's maritime security.

Chinh arrived in Delhi on Tuesday night on a three-day visit that is aimed at further expanding the comprehensive strategic ties between the two countries.

"We have adopted a new plan of action to further strengthen our comprehensive strategic cooperation," Modi said in his media statement in presence of Chinh.

Modi said both sides will continue cooperation for a free, open, rules-based and prosperous Indo-Pacific.

Vietnam is India's important partner in our Act East Policy and Indo-Pacific vision, he said.

"We support development, not expansionism (Hum vistarbad nahi, vikasvad ka samarthan karte hei)," Modi said.

The comments came amid growing global concerns over China's expansionist behaviour in the Indo-Pacific.

Modi said various dimensions of India-Vietnam relations have both expanded and deepened in the last one decade.

In the last 10 years, we have transformed our relations into a Comprehensive Strategic Partnership, he said.

"We held extensive talks on all aspects of mutual cooperation and initiated steps towards the framework of future cooperation," he said, adding the two countries have adopted a new plan of action to further strengthen comprehensive strategic cooperation.

Modi said both sides have decided that cooperation will be strengthened on counter-terrorism and cyber security.