Medical officials in the Gaza Strip said multiple Israeli airstrikes have killed at least 14 people in the past 24-hour period of cross-border fire, which was triggered on Friday when an attack killed the leader of a militant group in the area.

The Israeli military said it initially targeted Zuhair al-Qaissi, the commander of the armed wing of the Popular Resistance Committees (PRC) - an umbrella group of activists and militants from various Palestinian factions. Al-Qaissi was killed while travelling in a blue car with his son-in-law Mahmoud Hanini, himself a senior PRC member.

The PRC is thought to be the group that orchestrated the kidnapping of Israeli soldier Gilad Shalit, who was held captive for five years before being released last October. Al-Qaissi had led the group for less than a year. His predecessor Kamal Nairab was killed in a similar strike seven months ago.

Military officials said al-Qaissi had been planning an infiltration into Israel from its border with Egypt "in the coming days."

In response to the killing, the PRC is said to have sought retaliation, with several groups reportedly firing at least 70 rockets.

Israel's armed forces later said it had conducted multiple airstrikes on Palestinian territory, including the initial attack, targeting those seeking to retaliate.

The restive region in the Middle East had been relatively quiet in recent weeks, with the last known lethal Israeli air raid in the Gaza Strip having taken place in mid-January.

At least a dozen people have been injured in the new violence, which is the worst so far this year.

msh,sb/slk (AFP, AP, Reuters)