"The behind-the-scenes calls with us by great powers, Arab countries, envoys of the United Nations, directly and indirectly telling us not to interfere will have no effect," he told supporters gathered in the southern Beirut suburb for a rally.

"Hezbollah knows its duties perfectly well. We are prepared and ready, fully ready," Qassem said.

The group has already clashed with Israel across the Lebanese border multiple times in the past week in the deadliest confrontations since they fought a month-long war in 2006.

The cross-border rocket fire and shelling followed the assault by Palestinian faction Hamas against Israeli towns and Israel's retaliatory bombardment of the Gaza Strip.

But sources say Hezbollah has designed its moves so far to be limited in scope, preventing a big spillover into Lebanon while keeping Israeli forces occupied.

"The question being asked, which everyone is waiting for, is: what Hezbollah will do and what will its contribution be?" Qassem said. "We will contribute to the confrontation within our plan... when the time comes for any action, we will carry it out."

Qassem spoke at a rally where hundreds of people had gathered in solidarity with Palestinians, waving the flags of Palestine and of Hezbollah.

Other rallies were organized in Palestinian camps as well as cities across southern and eastern Lebanon where Hezbollah has a strong presence. Fearing a breakaway group might try to cross the border, the Lebanese army deployed units across the south.

Hezbollah chief Sayyed Hassan Nasrallah has not yet commented on developments. He met on Friday morning with Iranian foreign minister Hossein Amirabdollahian to discuss the conflict between Israel and Hamas.

Amirabdollahian said on Thursday that Iran's allies in the region would respond to Israeli "crimes" against Palestinians, and that Israel would then have to bear the consequences.