Palestinian relatives react during funeral of militant Fuad Abu Marouf  in Jebaliya refugee camp, northern Gaza Strip, 07 Apr 2007

An Israeli helicopter launched an air strike along the Gaza border, firing missiles at Palestinian militants whom the army said were planting a bomb. Residents described it as the fiercest attack since a ceasefire went into effect more than four months ago.

The air strike came a few days after Israel's defense minister authorized limited strikes just inside Gaza to try to stop militants from planting explosives, digging tunnels and firing rockets across the border. Dozens of rockets have been fired since the truce began, and the army says Palestinians have planted 40 bombs along the border fence.

Palestinian analyst Wadia Abu Nasser says the Palestinian Authority has not been able to control militants violating the truce.

"I tell you frankly, I think it is quite difficult to implement the ceasefire totally, especially due to the fact that we are talking about a lot of small cells which are not obedient to anybody," said Abu Nasser.

Israel says groups like Hamas and Islamic Jihad have been exploiting the truce to smuggle explosives, missiles and other weapons into Gaza through tunnels from neighboring Egypt.

"The challenge is clear," said Israeli spokesman Mark Regev. "You have a situation where you have extremist groups inside Gaza, who are seeking to upgrade their terrorist capabilities, to upgrade their strategic capabilities, and try to get weaponry, state-of-the-art hardware. And, of course, it is not in our interest for that to happen."

Fearing that Gaza could pose a strategic threat to Israel, the army has been planning a major offensive. But the political leadership is reluctant to authorize it because of the likelihood of high casualties among both soldiers and Palestinian civilians.

There is no ceasefire in the West Bank, where the Israeli military has continued almost daily raids against wanted militants. In a clash at the Jenin refugee camp, troops shot and wounded Zakariye Zubeydi, the local leader of the al-Aqsa Martyrs Brigades.