JERUSALEM, May 18 (Reuters) - Israel on Wednesday criticized a UN envoy for blaming Israeli forces for the fatal shootings of 10 Palestinian protesters at a demonstration on Sunday at the Lebanese frontier, saying he had rushed to judgment.

Michael Williams, the UN special coordinator for Lebanon, said on Monday Israel had used disproportionate, deadly force during the demonstration by Palestinians on the day they mark what they term the catastrophe of Israel's founding in 1948.

The overhasty statements by ... Williams, as quoted by the wires, are aggravating, Israeli Foreign Ministry spokesman Yigal Palmor said in a written statement.

Mr Williams' unbalanced statement does not reflect realities on the ground and does not contribute to efforts to return to calm, Palmor said.

The Lebanese army said Israeli soldiers fired at the demonstration at the Lebanese border village of Maroun al-Ras, killing 10 protesters.

Palmor said Lebanese soldiers had laid down deterrent fire in response to violent rioting by demonstrators who intended to breach Israel's border fence. His statement stopped short of directly accusing Lebanese forces of shooting the protesters or denying outright that Israeli troops had killed them.

Williams, according to Palmor, should have awaited the results of an investigation by UN peacekeepers in the area before jumping to conclusions and laying the blame on Israel.

Williams was not present at the site, and his remarks rely on Lebanon's announcements, he said.

(Writing by Allyn Fisher-Ilan; editing by Mark Heinrich)