Spain's second-biggest bank BBVA said Wednesday its first quarter net profit more than doubled in 2015 with a one-off boost from the sale of its stake in China Citic Bank Corp.

The Bilbao-based lender reported a net profit of 1.54 billion euros ($1.68 billion) during the first three months of the year, up from 624 million euros during the same period last year.

Analysts contacted by financial information provider Factset had predicted the bank would post a net profit of 1.37 billion euros.

BBVA said first quarter earnings were lifted by the January sale of its 5.6 percent stake in Chinese lender China Citic Bank Corp. to Chinese firm Xinhu Zhongbao.

Excluding that gain, the bank's net profit still rose 53 percent to 953 million euros.

BBVA's sale of its position in the Chinese lender was part of an effort to shore up its finances as European regulators toughen post-crisis capital requirements for banks.

The bank said its core equity tier one capital on a fully-loaded basis, a closely-watched measure of capital strength, now stands at 10.8 percent, up from 10.4 per cent at the end of last year.

Like its main rival Santander, BBVA saw its performance improve in its domestic market as Spain's economic recovery strengthened.

The bank's net interest income -- the difference between what lenders pay clients for deposits, and what they earn on loans -- rose 3.9 percent to 968 million euros in Spanish activity.

The indicator is a key driver of profit for retail banks.

BBVA said its acquisition last year of Catalunya Banc, a regional savings bank that was nationalised during Spain's 2012 banking crisis, had added 1.5 million clients to its Spanish network, which helped boost its revenues in the country.

"These results confirm the positive growth trend we have seen since the end of last year," BBVA president Angel Cano said in a statement.

The Spanish economy, the eurozone's fourth largest, fell into a prolonged slump when a property bubble burst in 2008, leaving thousands of labourers out of work and creating an aftershock that claimed millions more jobs across the country.

But the economy is in the midst of an accelerating economic recovery fuelled by a rise in private consumption and higher business investment.

Spain's GDP expanded by 1.4 percent in 2014 -- the first full-year of economic growth since the property collapse -- and Prime Minister Mariano Rajoy on Monday said the government expects the economy will expand by 2.9 percent this year.

The government had previously forecast 2.4 percent growth in 2015.

Santander, the eurozone's biggest bank, said Tuesday its first quarter net profit rose by 32 percent to 1.72 billion euros on the back of better lending income in Spain and fewer provisions against losses on bad loans.