Etisalat, the UAE-based telecoms operator, said on Wednesday it would block services to fake mobile phones from January 1.
The move follows a directive by the regulator, the Telecommunications Regulatory Authority, last month which ordered the UAE's telcos to crackdown on the estimated 70,000 counterfeit handsets believed to be in the country.
It also follows a similar decision by rival du announced on Tuesday to stop services to illegal phones from December 21.
Matthew Willsher, chief marketing officer, Etisalat, said: "Etisalat fully supports the TRA's decision in order to safeguard the interests of our customers as well as retailers.
"The use of fake mobile devices poses risks to users and adversely affects the quality of the telecommunication services."
Etisalat said in a statement that it has notified customers via SMS message alerting them about their use of fake mobile devices with a fake international mobile equipment identity (IMEI) number.
"In order to avoid disconnection of service, affected customers can replace their fake mobile devices with approved ones available from Etisalat."
UAE telco du said on Tuesday that it will block all unauthorised IMEIs from December 21.
UAE law prohibits the use, sale, purchase or distribution of fake mobile phones and those violating the law will be given notices and fines and in some cases their retail licences withdrawn, the TRA said.
There are some 11 million mobile phones in use in the country, it added.