* Liberman says Damascus must "pay the price" for attack
* Conflicting reports of Syrian victims of retaliation (Adds official Syrian statement, Israeli military source on number of Syrians killed)
JERUSALEM, June 24 (Reuters) - Israeli Foreign Minister Avigdor Lieberman said on Tuesday that Syrian forces launched an attack that killed an Israeli boy on the occupied Golan Heights and Damascus would have to "pay the price" for it.
An anti-tank missile fired from Syria across the frontier fence on Sunday killed Mohammed Qaraqara, 13, drawing Israeli tank fire and air strikes on Syrian army positions.
"We got all the analysis, all the intelligence and it was clear it was Syrian authorities, Assad's forces, who fired on the Israeli boy," Liberman said, referring to Syrian President Bashar al-Assad.
"They must pay the price," he told Israel Radio. "I hope Damascus got the message."
It was the first time an Israeli official has laid blame for the attack, which Israel had earlier described as intentional and the most serious on the frontier since the start of the three-year-old Syrian conflict.
The Syrian army has a presence on the Golan Heights but many areas are controlled by rebels, including militant groups hostile to the Jewish state.
There were conflicting accounts on the number of Syrians killed in the Israeli retaliatory air strikes late on Sunday.
The Syrian Foreign Ministry said four people were killed and nine wounded, according to state news agency SANA, and called on the U.N. Security Council to condemn the attacks.
An Israeli military source told Reuters on Monday that three Syrians were killed and 10 wounded. The Syrian Observatory for Human Rights, a monitoring group that collects information from activists in Syria, said "at least 10 members of the Syrian army were killed".
"I think Israel responded exactly as we should have, in this case and all others. We cannot just gloss over an Israeli citizen, a boy, being murdered in cold blood with no one being held responsible," Lieberman said.
The Syrian conflict has spilled over into bordering countries and escalated regional tensions. Shelling from Syria has occasionally hit the Golan, including what Israel has said were deliberate attacks on its troops.
Israel captured the western part of the plateau from Syria in a 1967 war and annexed it in a move that is not recognised internationally. (Additional reporting by Sylvia Westall in Beirut and Dan Williams in Jerusalem; Writing by Maayan Lubell; Editing by Tom Heneghan)