The leader of Lebanon’s Hezbollah said on Thursday the mass bombing attack against it using its communications devices was a “severe blow” and said Israel had crossed a “red line”.

But he said the group would continue its daily strikes into northern Israel, vowing Israelis would not be able to return to their homes there until the Gaza war ends.

As Hassan Nasrallah spoke in a televised speech from an unknown location, Hezbollah and the Israeli military traded new strikes over the border and at least two Israeli soldiers were killed.

Israeli warplanes also flew low over Beirut and broke the sound barrier, scattering birds and prompting people in houses and offices to quickly open windows to prevent them from shattering.

Fears are rising that 11 months of exchanges of fire between the two sides will escalate into all-out war, particularly after this week’s unprecedented bombings widely blamed on Israel in which hundreds of pagers and walkie-talkies used by Hezbollah were remotely detonated in Beirut, parts of Lebanon and the Syrian capital Damascus.

At least 37 people were killed and some 3,000 wounded in the explosions, which appeared to be the culmination of a months-long operation by Israel to target as many Hezbollah members as possible all at once, but which also hit civilians.

The attack came as Israeli leaders have warned that they could launch a stepped-up military operation against Hezbollah, saying they are determined to stop the group’s fire to allow tens of thousands of Israelis to return to homes near the border.

Nasrallah said the group is investigating how the bombings were carried out.

“Yes, we were subjected to a huge and severe blow,” he said. “The enemy crossed all boundaries and red lines,” he said. Pointing to the number of pagers and walkie-talkies, he accused Israel of intending to kill thousands of people at one time.

“The enemy will face a severe and fair punishment from where they expect and don’t expect.” He said Hezbollah will continue its barrages into northern Israel as long as the war in Gaza continues, vowing that Israel will not be able to bring its people back to the border region.