Modi was received at the Leh Airport by Governor N.N. Vohra and Chief Minister Mehbooba Mufti.
As separatists called for protest march to Srinagar's city centre Lal Chowk against Modi's visit, the authorities suspended mobile internet services across the Kashmir Valley as a precautionary measure, police said.
Restrictions were also imposed in several areas in Srinagar. All schools and colleges were shut for the day.
Separatists leaders, including Syed Ali Geelani and Mirwaiz Umer Farooq have been placed under house arrest while Yasin Malik has been taken into preventive custody.
The Prime Minister has a hectic schedule that includes the unveiling of a plaque to mark the commencement of work on the Zojila Tunnel, India's longest road tunnel and Asia's longest bi-directional tunnel.
The state-of-the-art Zojila Tunnel would provide all weather connectivity between the Ladakh region, that remains cut off from the rest of the country during the winter months.
It will cut down the time taken to cross the Zojila pass from three-and-a-half hours to just 15 minutes, besides providing all-round economic and socio-cultural integration of the region. It also has immense strategic importance, an announcement said.
Modi would also attend the closing ceremony of the birth centenary celebration of Buddhist spiritual leader Kushok Bakula Rinpoche in Leh.
He will also dedicate the 330 MW Kishanganga hydropower project to the nation, at the Sher-i-Kashmir International Conference Centre (SKICC) in Srinagar during the day. Besides, laying the foundation stone of the four lane 41.2-km long Srinagar Ring Road.
In Jammu city, Modi will lay the foundation stone of the Pakul Dul Power Project and the four lane 58.2-kilometre-long Jammu Ring Road.
Ring Roads in Srinagar and Jammu are aimed at reducing traffic congestion and making road travel safer, faster, more convenient and more environment friendly.
Modi will also inaugurate the Tarakote Marg and Material Ropeway of the Shri Mata Vaishno Devi Shrine Board that will facilitate pilgrims visiting the shrine.
The Prime Minister will also attend the Convocation of the Sher-e-Kashmir University of Agricultural Sciences and Technology in Jammu.
After a busy day, Modi will fly back to New Delhi in the evening.