Security sources said a bomb destroyed the car of an official, Hussein Assaf, seconds after he and his bodyguard left the vehicle and went into the house of senior Hizb Allah leader Shaikh Muhammad Yazbek in the ancient town of Baalbek, a Hizb Allah stronghold.
"We blame the Zionist enemy for planning and executing this attack," a spokesman for the Lebanese Shia resistance group said in a statement after the explosion on Friday.
Hizb Allah fighters cordoned off the roads leading to the blast site.
"The Islamic Resistance (Hizb Allah's military wing) will bear its responsibility ... and do what is necessary to defend its people," the statement said.
Hizb Allah said the explosion was an implementation of Israeli threats.
"The blast is a translation of the announced and repeated threats by the Zionist enemy's officials," it said.
Israeli officials denied any military involvement in the incident.
Hizb Allah, which is backed by Syria and Iran, has in recent years accused Israel of killing two of its officials in similar attacks. Israel has denied any part in those killings.
"We blame the Zionist enemy for planning and executing this attack"
Hizb Allah spokesman
Hizb Allah attacks were a factor behind Israel's decision to pull its troops from south Lebanon in 2000, ending 22 years of occupation.
The Beirut government has been unable to disarm Hizb Allah as demanded by a United Nations Security Council resolution in 2004.
Hizb Allah says it would not disarm even if Israel withdrew from the occupied Shebaa Farms.
Syria, Lebanon and Hizb Allah say the farms, on the foothills of the Golan Heights, are Lebanese.