Jerusalem ? A long-sought truce between Israel and Gaza militants went into effect early today, with the aim of halting militant attacks and a bruising Israeli blockade that have made life unbearable for people living on both sides of the border.

A day of intense Palestinian rocket and mortar fire and Israeli air reprisals on Wednesday underscored just how fragile the Egyptian-brokered agreement would be. Hamas security reported that the Israeli navy fired four shells into the waters off Gaza City after the truce began; the military had no immediate comment. Hamas has run the territory since seizing control a year ago.

There were no other reports of fire.

Although each side has expressed skepticism over the other’s commitment to the accord, the hope is that it will avert an Israeli military invasion of the tiny seaside territory it pulled out of nearly three years ago.

Just a day before the cease-fire was set to take hold, Israel launched another diplomatic initiative – a public call on neighboring Lebanon to open peace negotiations. Lebanon’s premier quickly rejected the call.

The Gaza deal, which took effect at 6 a.m., is supposed to last six months. According to its terms, militants will immediately halt their attacks on Israel, and Israel will cease its raids.

After three days, Israel is to ease its blockade of Gaza to allow the shipment of some supplies to resume. A week later Israel is to further ease restrictions at cargo crossings. In a final stage, the sides are supposed to talk about opening a major border passage between Gaza and Egypt and the release of an Israeli soldier Hamas has held for two years.

Israel’s blockade was imposed in an effort to pressure Hamas to stop attacks from Iranian-backed militants, who have been bombarding southern Israel with rockets and mortars for seven years.

The rate of fire increased after Israel pulled its troops and settlers out of Gaza in 2005 and stepped up further last year after Hamas wrested power from forces loyal to moderate Palestinian President Mahmoud Abbas, whose government controls the West Bank.