Iranian President Hassan Rouhani, Afghan President Ashraf Ghani and Indian Prime Minister Narendra Modi have signed a three-way transit agreement on Iran's southern port of Chabahar.

The accord calls for joint investments and will significantly boost the role of the undertapped port of Chabahar. It will be developed to connect Iran through India and Afghanistan to central Asia.

Modi arrived in Tehran on Sunday for talks on economic cooperation with Iran. It's the first visit by an Indian leader to Iran in 15 years. The two sides signed 12 memorandums of understanding to expand ties in diverse fields. They also agreed to pursue political dialogue and collaborate on science and technology and cultural programs.