Hand-held communication devices have detonated across Lebanon for two days in a row, raising concern that the conflict between the Lebanon-based Shia Muslim group Hezbollah and Israel may escalate.

On Wednesday portable radio devices detonated in many places in Lebanon. Health authorities say 20 people were killed.

The incident came a day after pagers exploded on Tuesday, leaving 12 dead. In total, 32 people died and more than 3,000 were injured in the explosions over the two days.

Hezbollah has blamed Israel for the explosions and hinted at a retaliatory attack. They say their leader Hassan Nasrallah will release a statement on the attacks on Thursday evening.

The Israeli government has made no public comment on the series of explosions. But Defense Minister Yoav Gallant indicated a build-up of forces along the Lebanon border.

Gallant was quoted as saying on Wednesday, "The center of gravity is moving north," adding that "we are at the onset of a new phase in this war."

Prime Minister Benjamin Netanyahu stressed in a statement that the residents who had evacuated from the country's north due to the fighting with Hezbollah will be able to safely return to their homes.

Israeli media have reported that the military has moved some units to the north.

Meanwhile, some reports say products of a Japanese communication device maker based in Osaka may have been used in Wednesday's explosions.

Manufacturer Icom says the production and export of the two-way radio devices was discontinued about 10 years ago.

It says the speed of the automated manufacture of the devices would have left no time to put explosives in them.

The company says many counterfeit products are on the market, and that it hopes to confirm whether the devices in question were actually its own products.