Dozens of Irish technology companies are in Spain this week for the world's largest mobile communications industry trade fair and conference.

Tens of thousands of industry executives are attending meetings, product launches and sales events at the Mobile World Congress in Barcelona.

Over the next four days, more than 75,000 people will visit the event to learn about emerging trends, meet contacts and showcase new products.

Sony was first out of the gate with a new flagship smartphone that features 4k video recording and digital noise cancelling headphones.

The Xperia Z2 also has the first ever Phosphor LED display, which is 13.2cm in size.

Nokia also used the conference to confirm it is moving into the Android mobile phone market.

The Finnish company has revealed the Nokia X, which has a 10cm screen and 3MP camera, the Nokia X+ and a larger Nokia XL, which has a 14cm display and 5MP camera.

The Nokia X phones, which have the ability to run Android apps, will retail from €89.

Mobile device manufacturer Samsung has unveiled a number of new flagship products at the Congress, including a high-end smartphone and a fitness tracking device.

The Galaxy S5 smartphone is waterproof and dust resistant and features a finger print scanner and heart rate monitor. 

It also boasts an improved 16MP camera and 2.5Ghz Quad core processor. The new device, however, looks similar to its predecessor, the Galaxy S4, which was launched a year ago. 

Samsung also announced details of a new wrist wearable fitness tracker, the Gear Fit. It features a curved 1.8 inch AMOLED screen, through which the user can monitor pedometer, exercise, heart rate and sleep apps. It is also dust and water resistant. 

Like its Galaxy Gear 2 sister, the Fit can also be used to answer calls, send emails and control media, when paired with compatible Galaxy smartphones. According to Samsung, its battery will last 3-4 days on a single charge with typical usage.

There will be plenty of discussion of the future, with wearable technology, the internet of things and in-car technology all likely to be dominant themes.

Around 50 Irish companies will also be showcasing their products, including 18 early-stage and established Enterprise Ireland clients.

But perhaps most attention today is focused on keynote speaker, Facebook founder Mark Zuckerberg.

Mr Zuckerberg described social messaging service WhatsApp, which Facebook recently purchased for $19bn, as a great company and a great fit for Facebook.

WhatsApp has said it will begin offering voice services in the near future.

He said WhatsApp is incredibly valuable to his company Facebook because it is on a path to having 1 billion users.

Speaking at the Congress, Mr Zuckerberg said the messaging app that Facebook bought last week for $19bn is a great company and a great fit for the social network.

He also said WhatsApp policy towards data storage and use is absolutely not going to change following the takeover.

He said not only does WhatsApp not use the content, they do not even store it. That is the service people want, and it would be silly to get in the way of that, he added.

He said WhatsApp would operate autonomously of Facebook, but use some of its services.

On the issue of government surveillance on the internet, he said governments blew it. He said governments have a responsibility to protect people and be transparent, but they went way over the line on transparency. He added that we are only now starting to get to the range of where they should be on transparency.

Talking about his new organisation,, which aims to bring the internet to the developing world, Mr Zuckerberg said he wants it to become an "on ramp to the internet".

Asked by a member of the audience if Facebook would consider another bid for Snapchat, Mr Zuckerberg said he would make no comment, but then added that after buying a company for $16bn, "you are probably done for a while".

Speaking earlier in Barcelona, WhatsApp Chief Executive Jan Koum said the service will introduce voice in the second quarter of this year.

The service will first be offered to iPhone and Android users, before it is spread to those using other operating systems.

Mr Koum said WhatsApp's goal is to be on every mobile phone in the world. It is already being used by 450 million worldwide.

RTÉ's Science and Technology Correspondent Will Goodbody is attending the Mobile World Congress.

Follow him on Twitter @WillGoodbody