Beware, your mobile's buzz in banks in Patna may land you in trouble.

Alarmed by rise in the incidents of bank robbery in Bihar, the state police has warned of penal action if its directive to switch off the mobile phones while entering banks in the state capital is not being strictly adhered to.

A decision to ban the use of the mobile phones was taken at a meeting of senior police officials with representatives of various nationalised and private banks on Monday, City Superintendent of Police Vikas Vaibhav told PTI on Tuesday.

Now closed-circuit cameras will be installed at the main entrance of the banks, at the cash counters and the strongrooms, he said.

"The bankers have been asked to make people aware of the new directive through banners and posters," he said.

The ban was being imposed with investigations revealing that in most of the cases of bank robbery, the criminals used their cellular phones, he said.

Henceforth, a police officer with a constable will escort the bank staff carrying cash from one branch to another on a two-wheeler, regardless of whether the amount was big or small, Vaibhav said.

Armed criminals had recently looted Rs 50 lakh from bankers going to deposit the amount in the chest of the Punjab National Bank [Get Quote] at Patrakarnagar in Patna and Rs 38 lakh of the State Bank of [Get Quote] Bikaner being brought from Muzaffarpur for deposit near Sarai railway crossing in Vaishali district.

In another incident, Rs 22 lakh was looted from the United Bank of India [Get Quote] branch in Samastipur last month.