Palestinian militant group Islamic Jihad vowed Tuesday to retaliate for its recent losses from Israeli air strikes with suicide attacks inside Israel, threatening "a wave of martyrdom operations" in an e-mail to reporters.

If such threats are carried out, it would end a relatively tranquil period of 11 months that have featured an absence of suicide bombings in the country.

Meanwhile Tuesday, the Israeli military resumed air strikes targeting both Islamic Jihad and members of Islamist movement Hamas in the Gaza Strip, killing at least six militants a day after similar attacks killed six others — including the radical group's overall commander. 

Four Islamic Jihad members were killed as they left morning prayers Tuesday at a northern Gaza mosque, witnesses and officials said.

Another air strike Tuesday on a Hamas post in southern Gaza killed two Hamas members, said officials from the Islamist group, which seized control of the coastal territory from rivals Fatah in June.

The air strikes come amid intense political pressure on Israeli Prime Minister Ehud Olmert's government to order a large-scale military operation in Gaza to clamp down on daily rocket attacks on Israeli border towns fired by militants from the Hamas-controlled territory.

Thousands march at funerals

Six militants died Monday night when Israeli aircraft blasted two cars in Gaza City, including one filled with a large amount of explosives that triggered a huge blast, according to Palestinian figures.

Among the dead was Majed Harazin, a senior Islamic Jihad militant in charge of rocket squads that have been firing at Israel, group spokesman Khaled el-Batch said.

The Israeli military said it was targeting Harazin, who was reportedly on Israel's wanted list for the past nine years and rarely travelled in a vehicle for fear of an Israeli air strike, according to the militant group.

"There is no doubt that this is a big loss," Khader Habib, an Islamic Jihad leader in Gaza, told the Associated Press.

Thousands of Gazans took to the streets in funeral processions for the dead militants, whose bodies and coffins were draped with black Islamic Jihad flags. In northern Gaza, bullets from the rifles of mourners severed an electric wire, which fell, injuring five people, medics said.

Meanwhile, militants fired at least five homemade Qassam rockets and two mortar shells early Tuesday at a border crossing between Gaza and Israel, but no injuries were reported, according to Israeli newspaper Haaretz.  

Islamic Jihad, a small radical group with ties to Iran, has taken responsibility for most of the rocket barrages, including one that lightly wounded a two-year-old boy in an Israeli village this week.

With files from the Associated Press