BEIJING - China on Saturday said it is "deeply concerned" by the escalating Ukraine crisis with violence and clashes causing numerous casualties in east and south Ukraine.

"We call on all parties in Ukraine to stay calm and exercise restraint," Chinese Foreign Ministry spokesman Qin Gang said.

Qin's remarks came after the clashes in the Black Sea resort of Odessa killed at least 43 people and injured 174 others on Friday.

Earlier that day, two Ukrainian military helicopters were shot down when government troops tried to retake the eastern city of Slavyansk held by pro-Russian protesters, causing casualties on both sides.

Qin urged the concerned parties to back the Geneva agreements reached by Russia, the United States, the European Union and Ukraine on April 17, which called for an immediate halt of violence in Ukraine and practical steps to de-escalate the tension.

"We hope that all sides can give up the use of force or violence that could deteriorate the situation, and start political dialogue and reconciliation process as soon as possible, in a bid to ease the situation," Qin said.