Israeli warplanes struck four targets in the Gaza Strip on Friday in response to militant rocket and mortar fire, the Israeli army said.

Two other strikes were aimed at targets near the town of Khan Younis in the southern part of the territory, one of which was a training camp belonging to the Islamic Jihad militant group. There were no reports of casualties.

A fourth air strike late at night was aimed at a smuggling tunnel along the Gaza Strip border with Egypt where local residents said they heard two missiles explode but there was no word if anyone had been hurt.

An Israeli military spokesman said the air strikes had been carried out against militant targets in the coastal strip in response to the militant rocket and mortar fire.

He added that nine mortar shells and one longer-range rocket were fired over the past 24 hours, the highest number in a concentrated period for several months.

The Popular Resistance Committees, a Palestinian militant group, claimed responsibility for the mortar fire, saying it was in retaliation for Israel's killing of two militant leaders of the al-Qaeda linked Army of Islam in Gaza on Wednesday.