The crisis in Ukraine intensifies.

Pro-Russian rebels shot down two Ukrainian helicopters on Friday, trying to retake separatist-held Slaviansk.

Kiev said two helicopter crew had died and seven servicemen had been wounded in the operation.

Separatists said Ukrainian forces killed three of their fighters and two civilians.

Ukraine's acting president is again calling for an end to this violence:

(SOUNDBITE) (Ukrainian) OLEKSANDER TURCHINOV, ACTING PRESIDENT OF UKRAINE, SAYING:

"We demand the terrorists, saboteurs, all those who took up arms against our country to lay down their arms, surrender, release hostages and administrative buildings."

On the other side of Ukraine, violence erupted between pro-Ukrainian and pro-Russian activists in Odessa.

Police said 38 people were killed in a building fire here, three people were shot dead and 15 others were wounded.

The escalating violence is resonating across the globe. An issue German Chanc