Niger has cancelled 1.7 million mobile phone numbers, around one third of the West African country's total cell numbers, in what the government said was an attempt to improve security.
State telecoms regulator ARTP had previously asked mobile phone users to identify themselves by a Nov. 24 deadline, or face being cut off.
Boubacar Almoustapha, head of ARTP, said the cancellations would help "fight against various forms of insecurity".
The country has 5.4 million mobile users, he added.
Subsidiaries of Bharti Airtel, the country's biggest operator, and France Telecom's Orange were the most impacted by the move, with 916,701 and 628,407 affected customers respectively.
Moov, a local unit of United Arab Emirates' top telecom company Etisalat, and SahelCom, a subsidiary of state telecoms firm SONITEL, had a lower number of cancellations.
Niger's government said on Thursday it had arrested a man who was preparing attacks on two strategic locations in the capital Niamey. A spokesman said the man, identified as Beidari Mouloud, was stopped by authorities while attempting to board a bus for neighbouring Mali.
French forces this week also arrested a Malian man wanted in Niger for killing a U.S. diplomat in 2000 and convicted for a deadly attack on Saudi tourists there in 2009.
Niger has emerged as a firm ally of France and the United States in the fight against al Qaeda-linked groups in the Sahel Region. It deployed 650 troops in neighbouring Mali in a French-led campaign to drive out Islamist militants who had occupied northern Mali.