Keppel Corporation shareholders will reap an extra payout this year in the form of a special dividend to mark the group's 50th anniversary.

It announced the five-cent-per-share payment when releasing second-quarter results yesterday.

The payout will come on top of the interim dividend of 10 cents a share declared for the first half, up on the eight cents a share for the same period last year.

The firm also announced a boost in second-quarter net profit thanks in part to stronger property and infrastructure earnings offsetting losses from the other divisions.

Earnings rose 44 per cent to $246.16 million over the same period last year while revenue dipped 2 per cent to $1.52 billion for the three months to June 30.

Lower contributions from property and investments divisions more than offset higher turnover from offshore and marine (O&M) and infrastructure divisions.

First-half net profit was 38 per cent higher at $583.63 million.

Earnings per share for the quarter was 13.6 cents, up from 9.4 cents a year earlier.

Second-quarter earnings from its property unit surged 132 per cent while infrastructure was up 60 per cent.

These more than offset the $17 million net loss in O&M and investments, which slipped into the red to the tune of $2 million.

Chief executive Loh Chin Hua pointed to "cyclical headwinds in some businesses" but added that the group has remained resilient due to its "multi-business strategy and geographical diversification".

The group had to grapple with property cooling measures in Singapore and China.

Mr Loh said that the new measures here are still "playing out" so it was too early to say if the firm's plans for its Nassim Woods and Keppel Towers projects would be affected.

He acknowledged that Keppel Corp has "to deal with cooling measures" in certain cities in China, but expressed confidence in the demand-supply fundamentals of most of these markets.

It is set to book a $114 million gain from the sale of a 51 per cent stake in the Beijing Aether Property Development, the holding company for a prime commercial site. That is expected to materialise in the third quarter.

Mr Loh added that the property division is better able to stomach such regulatory changes given its geographically diversified footprint that extends to countries such as Vietnam and Indonesia.

He was cautiously optimistic about improved market conditions in the O&M unit, always a cyclical business.

The number of floating production projects awarded over the past year has increased with growing optimism in the sector and Brent crude prices hovering above US$70. But the recovery that is "expected to continue" would take "an incremental pace".

Keppel O&M had secured over $1.2 billion of new orders as at June 30, slightly more than the new orders it secured for the whole of 2017. Its net order book was $4.6 billion, excluding Sete Brasil projects, compared with $3.9 billion as at Dec 31, 2017.

Keppel Corp shares closed up 11 cents at $6.96 yesterday, before the results were released.