Two Israeli soldiers and one Spanish U.N. peacekeeper were killed in a clash between Israel and a Lebanese Hezbollah group.

Reuters reported that the soldiers were killed when Hezbollah fired missiles at their military convoys on Wednesday. The attack was carried out by a group called "righteous martyrs of Quneitra," and is likely in retaliation for an Israeli airstrike last week, which killed six Hezbollah fighters in Syria.

BBC News noted that the Spanish peacekeeper killed was close to the military vehicle that was hit.

In addition to the deceased, a handful of other soldiers were wounded, but their injuries are said to be minor.

Israeli Prime Minister Benjamin Netanyahu vowed that the country would respond to the attack "forcefully” and fired dozens of artillery shells into southern Lebanon.

United Nations Interim Force in Lebanon said that the peackeeper’s death is under investigation. Their name, as well as the identities of the soldiers, have not been released.

The attack is the deadliest between the two sides since the war in 2006.