OAK BROOK, Ill. » A Monopoly promotion and strong sales of basic menu items such as the Big Mac helped push a key sales figure up 5.6 percent in the U.S. for McDonald’s Corp. during October.

Its increase in sales at stores open at least 13 months was a marked improvement from the same month last year, when the metric dipped 0.1 percent in part because of tough comparisons. It was only the third time the monthly figure hadn’t climbed in 6 1/2 years.

The world’s biggest hamburger chain said yesterday that worldwide sales at restaurants open at least 13 months climbed 6.5 percent. That was slightly above McDonald’s prior forecast for an increase between 5 percent and 6 percent.

This figure is a key indicator of a restaurant operator’s health because it gauges results at existing restaurants rather than newly opened ones.

In the U.S., McDonald’s said other popular menu items included Chicken McNuggets, McGriddles and McCafe beverages, all of which came with pieces for the Monopoly game.

The Oak Brook, Ill.-based company has outpaced rivals like Burger King Corp. and Wendy’s/Arby’s Group Inc. in the weak economy partly because of its low-cost value menu items.

McDonald’s success has not been limited to the U.S. Monthly results were also healthy in Europe, where the sales metric climbed 5.8 percent. Among the strongest-performing countries were France, the U.K. and Russia.

The figure increased 5.6 percent for the Asia/Pacific, Middle East and Africa, with Japan, China and Australia reporting sales growth.

McDonald’s said its international results were helped by offering customers convenience, value and a variety of menu choices.

McDonald’s systemwide sales rose 7.4 percent for the month ending Oct. 31. On a constant currency basis, these sales increased 7.8 percent.

For the year to date, U.S. sales at restaurants open at least 13 months climbed 3.8 percent. The figure rose 4.9 percent for Europe and gained 6.1 percent for the APMEA region. McDonald’s total sales for restaurants open at least 13 months increased 5.2 percent.

Systemwide sales gained 7.5 percent for the year to date, or 6.6 percent on a constant currency basis.

McDonald’s has more than 32,000 restaurants in more than 100 countries.