"We denounce this massacre. We do not denounce simply by words, but by acts. The resistance does not talk, it acts," Meshaal said from his base in Damascus.
"I am expressing the political position (of Hamas): the heroes of the resistance on Palestinian land and all of our people will respond by acts," he said.
Eighteen Palestinians, including women and children, were killed Wednesday after Israeli shells damaged five homes in Beit Hanun in an attack condemned by the international community and Palestinian leadership.
Meshaal called for Israeli leaders to be tried for "war crimes" over the shelling.
"Israel has committed crimes for decades ... The Arab nation should demand to put the leaders of the enemy (Israel) before an international tribunal for war crimes," he said.
"The Zionists have surpassed all that the Nazis committed during the 1930s and 1940s," charged Meshaal, whose movement has respected a de facto truce on suicide attacks inside Israel since early 2005.
Meshaal said the "Zionist entity and American administration" were responsible for "these odious massacres".
"Hamas and the resistance movements will express our solidarity with Beit Hanun in words and with acts. We will stand at their side until victory and until we put an end to the unjust occupation," he said.
Meshaal was among three Hamas officials -- all Jordanian citizens -- who were expelled from the kingdom in 1999 after being accused of threatening its security and stability.
Two years earlier, Jordan saved Meshaal's life when officers of Israel's Mossad foreign intelligence service carried out a botched attempt to poison him in Amman.
Then-king Hussein secured the antidote from Israel with a threat to sever the kingdom's 1994 peace treaty with the Jewish state.
Jordan has had a sometimes rocky relationship with Hamas, which does not recognise Israel and is boycotted as a terrorist organisation by the European Union and United States.

Copyright AFP (Agence France-Presse), 2006