* Revenue of 7 pct higher than analyst estimates of 0-5 pct

* Revenue gains come after two new casino openings

* Analysts wary of sustainability of uptick

* VIP growth due to new credit issued

HONG KONG, Oct 1(Reuters) - The world's biggest casino hub of Macau posted a better than expected 7.4 percent rise in gambling revenue in September, marking the second consecutive month of growth after more than two years of decline, as new resorts spur spending in the southern Chinese territory.

Multi-billion dollar casino openings by Sands China Ltd and Wynn Macau Ltd helped attract VIP customers whose numbers have dwindled in the former Portuguese colony since the start of 2014 when the government began a campaign against shows of wealth by public officials.

A specially administered region of China, Macau is the only place in the country where casino gambling is legal. Revenue has fallen to five-year lows but has ticked up since the openings in August and September.

Gambling revenue in September was 18.4 billion patacas ($2.3 billion), government data showed on Saturday. The forecasts were higher than analyst estimates, which ranged from unchanged on the year to a 5 percent rise. While growth edged up from last month's 1 percent, overall revenue was still relatively muted.

Analysts said the boost was due to casino credit being extended to wealthy gamblers to encourage big betting in the new properties, but they questioned how long the uptick would last.

"We are concerned with the sustainability and quality of the gross gaming revenue improvement," said Nomura analyst Richard Huang. Revenue from mass market players had failed to grow significantly and new increases were from low-income VIP players, he said.

Growth in the VIP segment is typically more volatile than the mass market segment and can cause large swings in overall revenue. To reduce reliance on high-rollers, the national and Macau governments have been adamant that the tiny territory would diversify into general leisure and tourism.

Overnight visitors have grown since August due to operators attracting customers with cheaper hotel rooms and promotions but individual spending is muted.

Looking ahead, analysts said a rebound in spending remains a challenge despite new attractions including a mock Eiffel tower and aerial gondola, due to slowing market growth and infrastructure bottlenecks which hinder larger visitation into Macau's teeming peninsula and glitzy Cotai strip.

(Reporting by Farah Master; Editing by Christian Schmollinger)