Saudi troops enter Bahrain.

More than 1000 troops and hundreds of armored carriers from allied oil emirates have crossed into Bahrain to support and bolster that country's teetering monarchy confronted with a growing popular revolt.

The troops intervened in the embattled nation of a half-million people under the banner of the Gulf Cooperation Council after weeks of pro-democracy demonstrations turned larger and more violent in the last few days. The full size of the force is not known yet.

The ruling Bahrain monarchy says the forces will be used for purely defensive purposes like guarding infrastucture.

The Wall Street Journal reports:

Bahrain's opposition groups condemned the arrival of the troops as "a flagrant occupation of the country" that means "the people of Bahrain are in grave danger of a war being launched by an outside armed military without a formal declaration of war."

The opposition groups—who are mainly drawn from Bahrain's Shiite Muslim majority, while the ruling family is Sunni—said they would write in protest to United Nations Secretary-General Ban Ki-moon and the permanent members of the U.N. Security Council. The Gulf Cooperation Council comprises Saudi Arabia, Kuwait, the United Arab Emirates, Qatar, Oman and Bahrain.

The Saudi deployment comes on the heels of a damatic escalation of protests this past week, events overshadowed in the international media by the quake in Japan.  Police firing tear gas and iive ammo lost control of a crowd tryin to block the central financial district.  As the troops moved in, protesters were still occupying that city district.

The Obama adminitration said the Saudi deployment was not an occupation or invasion and gave it guarded support.