Social networking giant Facebook has increased its user-base to a whopping 1.44 billion at the end of the first quarter, with most of them accessing the website on mobile phones.

Facebook released its quarterly earnings and said that monthly active users, a key figure for social networking sites, were 1.44 billion as of 31 March, representing an increase of 13% year-on-year. Meanwhile, mobile monthly active users rose 24% year-on-year to 1.25 billion.

Facebook's 1.44 billion monthly user-base is larger than the population of China, where 1.36 billion people reside at present.

Daily active users were 936 million on average for March 2015, an increase of 17% over last year. Daily active users on mobiles were 798 million on average for March 2015, an increase of 31% since March 2014.

The increase in number of users comes in line with its increased operating expenses for the quarter. Total operating expenses increase 83% from last year, with significantly higher spending on research and development, and marketing and sales.

"This was a strong start to the year," said Mark Zuckerberg, Facebook founder and CEO.

"We continue to focus on serving our community and connecting the world."

The higher expenses come as Facebook is trying to boost its service through a range of new software products. The company earlier acquired photo-sharing service Instagram, messaging service WhatsApp and virtual reality headset maker Oculus Rift.

In addition, it is developing a number of mobile apps linked to the social networking site. On 22 April, the company introduced a new app for Android mobile phones, named Hello, which enables users to see who's calling them, block unwanted calls and search for people and places.

The caller ID app is linked to the social networking website, and people will only see info they could otherwise find there.

Earlier, the company separated its messaging service from the official Facebook app, and launched it separately under the name Messenger. Facebook currently offers about 15 different apps on the Google Playstore with various capabilities. It is also actively developing a number of apps -- Paper, Slingshot, Mentions, Rooms, Facebook Groups, Riff -- which are all connected to the main social networking platform.