Shanghai's real estate investment market dipped in the first six months of this year and sentiment may remain slack in the second half, global property services provider DTZ predicted.

The transaction value of major real estate investment deals, or property acquisitions worth more than US$10 million each, totaled US$15.7 billion between January and June, compared to US$18.3 billion registered during the same period a year ago, DTZ said in a report released today.

"Though the drop seemed insignificant in the first half, we do expect entire en-bloc investment value to fall as much as 50 percent this year from 2013, when it reached an all-time high of US$57.1 billion," said Jim Yip, managing director of investment and advisory services at DTZ China. "A decelerating national economy, tightened credit at commercial banks, slower growth in office rentals, as well as an abundant supply of commercial real estate in the local market jointly contributed to the decline in the first half."

Overseas investment only accounted for 9 percent of the total value registered in the first six months, an historic low. It compared to a 43 percent share in the same period a year earlier and 24 percent in the second half of 2013, according to DTZ data.

By property type, offices still remained the most favored option among investors with 57 percent of transactions sealed in the first half being office buildings.