UPDATE 1-Australia's ASX boosts stake in IRESS

(Adds details)

SYDNEY, Nov 30 (Reuters) - Australia's securities market operator Australian Stock Exchange Ltd (ASX.AX) said on Friday it has increased its stake in local securities trading platform IRESS (IRE.AX) by about 5 percent to 17.7 percent.

The exchange said it had no plans to further increase its holding in IRESS.

Shares in IRESS, which has a market capitalisation of about A$990 million ($870 million), jumped 4.9 percent at A$8.72 a share, in an overall market up about 0.8 percent.

A spokesman for the Australian Stock Exchange said its holding had been diluted after IRESS recently issued new capital.

"We didn't consciously dilute our holding over the last few months. We wanted to restore it back to the level of ownership we were initially comfortable with," the spokesman said.

"It's been a well-performing investment for us," he said. ($1=A$1.14) (Reporting by Victoria Thieberger; editing by Jonathan Standing)