barack_obama_140.jpgWASHINGTON (AP) – The White House says it's "extremely concerned'' by the deteriorating situation in southern Ukraine. The U.S. and Europe have been focused on eastern Ukraine, near Russia, where pro-Russian separatists have been occupying buildings for weeks.

But the unrest has spread to Ukraine's southern port of Odessa, where Ukraine's government is seeking to re-establish control.

White House spokesman Jay Carney says the possible loss of Odessa underscores the need for an immediate de-escalation to the crisis. He's suggesting Russia still needs to follow through with its part of a diplomatic deal to de-escalate.

Riots in Odessa led to 46 deaths Friday when a government building was set on fire. Carney says Ukrainian authorities should launch a full investigation. He says the U.S. mourns with Ukrainians the heartbreaking loss of life.