Bulgarian authorities said on Friday a company based in Sofia had nothing to do with the delivery of exploding communications devices to Hezbollah.

Hundreds of pagers and walkie-talkies detonated across Lebanon on Tuesday and Wednesday, killing at least 37 people, wounding nearly 3,000 and generating panic.

Israel's army announced new strikes on Hezbollah targets in Lebanon on Thursday, as warning sirens rang out in northern Israel, indicating possible incoming fire.

Hezbollah chief Sayyed Hassan Nasrallah said Thursday that Israel will receive "just punishment" for the communications device explosions that killed 37 people and wounded nearly 3,000 over two days.

Israel will face "tough retribution and just punishment, where it expects it and where it does not," Nasrallah said in his first speech since the blasts, adding that he would not give further details of the place, timing or nature of Hezbollah's response.

The wave of deadly explosions of pagers and walkie-talkies carried by Hezbollah members in Lebanon has sharply heightened Pentagon concern about a potential ground war erupting in southern Lebanon between Israel and Hezbollah, the Wall Street Journal reported on Thursday.

U.S. Defense Secretary Lloyd Austin announced Thursday that he spoke Wednesday with Israeli Minister of Defense Yoav Gallant to “review regional security developments and reiterate unwavering U.S. support for Israel in the face of threats from Iran, Lebanese Hezbollah, and Iran’s other regional partners.”

French President Emmanuel Macron has held phone talks with Speaker Nabih Berri and caretaker Prime Minister Najib Mikati over the deadly explosions that rocked Lebanon on Tuesday and Wednesday.

The Iranian ambassador to Lebanon, who was injured in the exploding device attacks this week, has been transferred to Tehran, the Iranian Embassy said Thursday.

Ambassador Mojtaba Amani's general health is “very good," the embassy said in a statement. Amani along with some 90 injured Lebanese citizens were transferred to Tehran on Wednesday night, it added.

Spanish Prime Minister Pedro Sanchez on Thursday called for a de-escalation of the conflict in the Middle East, as Lebanon said 37 people had now been killed by booby-trapped hand-held devices.

"Today the risk of escalation is once more increasing in a dangerous way" in Lebanon, said Sanchez, at a news conference with visiting Palestinian president Mahmud Abbas.

United Nations Secretary-General Antonio Guterres has said that civilian objects should not be weaponized, in the wake of a deadly wave of explosions across Lebanon targeting pagers used by Hezbollah.

"I think it's very important that there is an effective control of civilian objects, not to weaponize civilian objects -- that should be a rule that... governments should, be able to implement," Guterres said Wednesday at a briefing at U.N. headquarters.

Doctors in Lebanon spoke of horrific eye injuries and finger amputations, a day after Hezbollah paging devices exploded across the country, killing 12 people and wounding up to 2,800.

"The injuries were mainly to the eyes and hands, with finger amputations, shrapnel in the eyes -- some people lost their sight," said doctor Joelle Khadra, who was working in emergency at Beirut's Hotel-Dieu hospital.