New Zealand telcos are focusing on restoring downed phone services in the Christchurch CBD to ensure those trapped under rubble can make calls.
Mobile services went down following the magnitude 6.3 earthquake which struck 10 kilometres from the CBD lunchtime yesterday.
Telecom New Zealand urged users to only place calls that are necessary to prevent congestion and preserve power.
"Overnight we have focused our efforts on restoring and maintaining cell sites in the CBD, so survivors trapped in the rubble who do have mobile phones can continue to keep in contact with rescue teams," the company said in a statement.
"All central city cell sites that are operational have been connected to generators to keep them running."
The telco has enabled free fixed and mobile calls through all 260 pay phones in and around the city.
It is also handing out mobile phones to emergency workers arriving on the scene.
Vodafone NZ said its mobile network was operational, but experiencing congestion to demand. It said that the power supply to the west of the Christchurch central business district had been restored, but there was no expected time on when the eastern side of the city would be restored. Mobile sites on that side of the city were on back-up, with some off the air because they had used up their power sources.
"Generators have begun to arrive, sites are already being brought back online with further sites being connected as the morning progresses. Additional mobile cell sites are on their way to the region to be used where necessary," the telco said.
The telco asked that people only use the phone network for emergency calls, instead texting for non-critical communications. It also asked that people keep mobile data usage, such as for Facebook, Twitter and email, at a minimum.
Vodafone New Zealand said earlier today that its fixed-line and broadband services had been cut for many customers across New Zealand's Canterbury region.
"We are working with the local power company and Civil Defence to maintain service," Vodafone said.
"We are focusing on restoring our core network services and a number of actions are underway to resume service."
Text message services between Vodafone, Telecom and 2degrees had also been affected due to network congestion.
The official death toll at the time of writing stands at 75, according to 7 News, with up to 300 missing.