Hezbollah chief Hassan Nasrallah has been killed, dealing a seismic blow to the Lebanese group that has been engaged in a year of crossborder hostilities with Israel.

Hezbollah’s statement on Saturday came shortly after Israel’s military said it had killed Nasrallah in an air strike on Beirut’s southern suburbs – a move that could destabilise Lebanon and trigger a regional war.

Nasrallah, who led Hezbollah for more than 30 years, is by far the most powerful person to be killed by Israel in weeks of intensified fighting with Hezbollah. The Israeli military said it carried out a precise air strike on Friday evening while Hezbollah leadership were meeting at their headquarters in Dahiyeh, south of Beirut.

The Lebanese Ministry of Public Health said six people were killed and 91 injured in the strikes, which levelled six apartment buildings. Ali Karki, the commander of Hezbollah’s Southern Front and other commanders were also killed, the Israeli military said.

Gaza-based Palestinian group Hamas condemned Nasrallah’s killing as a “cowardly terrorist act”.

Israel has shifted the focus of its operation from Gaza to Lebanon, where heavy bombing has killed more than 700 people, according to the Lebanon Health Ministry, after cross-border exchanges escalated over the past week. Most of the Lebanese deaths came on Monday, the deadliest day of violence since Lebanon’s 1975-90 civil war.