Lebanese pro-Iran militia Hezbollah congratulated Palestinian group Hamas on its massive surprise attack in southern Israel on Saturday but stopped short of declaring military support for the group, saying it was "assessing" the situation while in direct contact with Hamas leadership.

It also warned the government of Israel to "learn lessons from the Palestinian resistance" and said the Hamas operation attack was a "decisive response to the continuing crimes of the occupation."

Hamas launched Operation al-Aqsa Flood on Saturday, occupying towns in southern Israel, killing and capturing Israelis, including soldiers. It also launched thousands of rockets into Israel from the Gaza Strip.

Reuters said that at least 22 Israelis were killed and 545 injured, some in critical condition.

The attack was the largest attack Hamas has carried out against Israel in years and comes after months of deadly Israeli attacks in the occupied Palestinian territories, and stormings of the Al-Aqsa Mosque in Jerusalem by Israeli extremists.

In response to attacks from Hamas, Israel announced that it has launched "Operation Iron Swords," with Israeli forces fighting to reclaim territory in southern Israel.

Will Hezbollah join the fight?

The Hamas leadership called on all armed Palestinian groups, as well as "resistance groups" in the Arab world to join it in fighting Israel.

However, there has been no military operation as of Saturday afternoon by either Hezbollah or Palestinian factions in Lebanon.

"We are constantly in coordination, cooperation and are conducting meetings with Palestinian groups in Lebanon," a Hezbollah spokesperson told The New Arab.

A spokesperson for Hamas in Lebanon referred TNA to Hezbollah's statement when asked if Lebanese political factions would participate in the fighting.

Al-Arabiya TV reported on Saturday afternoon however, that Israel had deployed troops to its border with Lebanon.

The Hamas spokesperson declined to comment on whether his group had been given approval by Hezbollah to stage attacks from southern Lebanon, saying there had been "no new developments in this area."

There are armed Palestinian factions in southern Lebanon, some of which have launched rudimentary rockets into Israel in the past.

Hezbollah exercises security control over the southern part of Lebanon, including the regions bordering Israel.

The militia's stated goal is resistance to Israel, as well as liberation of both Lebanon and Palestine from Israeli occupation.

Last month, Israeli and Hezbollah officials exchanged harsh words, with both the Israeli Defence Minister and Hezbollah leader Hassan Nasrallah threatening to send each others' countries "back to the stone age."

Though escalating rhetoric and a series of provocative moves have increased tensions on the border, neither Hezbollah nor Israel have publicly signalled a desire to go to war with the other.