AHMEDABAD, India (Reuters) - India's anti-terror police have arrested four Sri Lankan nationals in the western Indian city of Ahmedabad for suspected links to the Islamic State, police said on Monday.

The arrests were made late on Sunday at the city's airport following a tip-off, said Vikas Sahay, the top police officer in Gujarat state where Ahmedabad is located.

"Preliminary investigations show they were in contact with a key IS leader known as Abu, who is currently based in Pakistan. Further investigations are continuing to uncover the full extent of the conspiracy," Sahay told reporters, giving only one name for the Islamic State leader.

The arrested individuals were identified as Mohammed Nusrat (33), Mohammed Nafran (35), Mohammed Faaris (27), and Mohammed Rashdin (43), all residents of Colombo, Sri Lanka, whose foreign ministry did not immediately respond to a request for comment.

Sahay said the Gujarat Police's anti-terrorism squad found an Islamic State flag in their possession, while analysis of two seized mobile phones showed various photographs and videos indicating that they were involved with the militant group.

The ATS also recovered three loaded pistols along with another Islamic State flag from a location near Ahmedabad, identified from photos in the mobile phones, Sahay said.

Police have registered a case under sections of the Unlawful Activities (Prevention) Act, the Indian Penal Code (IPC) and the Arms Act against the four suspects, the officer said.

(Writing by Shivam Patel; Editing by Sharon Singleton)

By Sumit Khanna