The absence of a full-blown war in Lebanon has been touted as a core U.S. achievement, but now Washington’s grip on the crisis appears more tenuous than ever.

BEIRUT, Sept 18 (Reuters) - Hand-held radios used by armed group Hezbollah detonated on Wednesday across Lebanon's south in the country's deadliest day since cross-border fighting erupted between the militants and Israel nearly a year ago, stoking tensions after similar explosions of the group's pagers the day before.

The strikes come after Hezbollah's leader vowed to take revenge on Israel who it accuses of an audacious attack on pagers and handheld radios.

Lebanon and Hezbollah have blamed Israel for the attacks on Tuesday and Wednesday that killed 37 people and wounded around 3,000, although Israel has not directly commented on the attacks, which security sources say were probably carried out by its Mossad spy agency.

Days after the attacks on Hezbollah with exploding electronic devices across Lebanon, Israel has struck a suburb of Beirut.

U.S., U.K. and United Nations officials urged restraint as tensions ramped up between Israel and Hezbollah in Lebanon. After days of escalating conflict, Israel carried out extensive airstrikes targeting Southern Lebanon on Sept.

The leader of Hezbollah vowed to retaliate for this week’s deadly attacks on the group’s communications devices