Since 1994, Nagorno-Karabakh, where heavy fighting between Azerbaijani and Armenian forces erupted Saturday, has existed in a tense limbo. AP explains what's behind the conflict:

HOW BIG IS THE AREA?

This mountainous region of Azerbaijan, with about 150,000 residents in an area of 12,000 square kilometers (4,400 square miles) — somewhat smaller than the U.S. state of Connecticut — has been under the control of local ethnic Armenian forces and the Armenian military since the end of a full-scale war that killed about 30,000 and displaced an estimated 1 million.

WHEN DID IT START?

Long-simmering tensions between Christian Armenians and mostly Muslim Azeris began boiling over as the Soviet Union frayed in its final years. Once the Soviet Union collapsed in 1991 and the republics became independent nations, war broke out. A 1994 cease-fire left Armenian and Azerbaijani forces facing each other across a demilitarized zone, where clashes were frequently reported.

WHAT'S HAPPENED SINCE?

International mediation efforts to determine the region's final status have brought little visible progress. The unresolved conflict has been an economic blow to Armenia because Turkey has closed its border with Armenia, leaving the country with open borders only with Georgia and Iran. Azerbaijan said Sunday that it had declared a unilateral ceasefire, but rebel leaders in the area said they were still coming under fire.

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This version corrects the number of residents in Nagorno-Karabakh to 150,000.