Indian PM Modi's visit officially kicked off Thursday afternoon with the premier's one-on-one talks with Putin, and a meeting with Russian business leaders.

Modi and Putin had also met Wednesday for over informal talks at dinner, which the Kremlin described as "very constructive and warm."

The Indian PM said on Twitter that his conversation with President Putin focused on Indian-Russian ties, calling it "fruitful."

Ahead of the trip to Moscow, Modi said he aimed to "deepen the cooperation between India and Russia in the economic, energy and security spheres" and called Russia "one of India's most valued friends in the world."

Putin and Modi are participating in a two-day summit - talks are expected to focus on defense, nuclear and space cooperation.

The leaders of India and Russia have hosted annual bilateral summits since 2000, as part of a strategic partnership agreed between Putin and India's prime minister at the time.

Russian defense systems

While President Vladimir Putin lauded Russian-India relations, he said the two nations were building a "privileged strategic partnership" in a possible reference to India's interest in purchasing Russia's advanced S-400 air defense systems.

India has remained a major customer for the Russian arms industry, while in recent years also buying military hardware from the United States, France and Israel.

Indian defense analyst Dipankar Banarjee told the AFP news agency that India's interest in Russian defense systems was due to its vulnerability to "Pakistan and China both in terms of missile and air strikes." He said the S-400 system was "very desirable" for New Delhi despite its huge financial cost.

Earlier this week, Russian newspaper Kommersant wrote that India could buy as many as five defense systems from Moscow.

Nuclear cooperation

According to Indian Foreign Secretary S. JaishankarJaishankar, Modi's talks in Moscow also included nuclear cooperation.

"We have a roadmap for nuclear cooperation with Russia, and we are moving in accordance with that," said Jaishankar.

Russia has built a nuclear reactor at the Kudankulam nuclear power plant in India and is now completing a second unit there. The two nations have a plan envisaging that Russia will build a total of 12 nuclear reactors in India over 20 years.

shs/rc (AFP, dpa, AP)