Guns went quiet as a six-month truce between Israel and Gaza Strip militants took effect early Thursday, but there was widespread skepticism about its ability to hold.

The cease-fire, which Egypt labored for months to conclude, aims to bring an end to a year of fighting that has killed seven Israelis and more than 400 Palestinians — many of them civilians — since the Islamic militant group Hamas wrested control of Gaza a year ago.

It also obliges Israel to ease a punishing blockade of the coastal strip. The sanctions were designed to pressure Palestinian militants to halt their rocket and mortar fire on southern Israel, but have driven ordinary Gazans even deeper into destitution and confined them to their tiny seaside territory.

“I want to be able to sleep without the sound of shelling or warplanes,” said Eman Mahmoud, a 22-year-old Gaza university student. “We have been living a nightmare. ... I am not sure how long it is going to last, but my dream is that this calm will continue.”

Tal Mahatzili of the southern Israeli farming community of Nir Oz said she was afraid the tranquility Thursday morning was “the quiet before the storm.”

“If I could believe our neighbors had stopped their hostile activities, washed their hands at 6:05 and went to the local library to draft a peace proposal, then I would say, “Wow,’ and heave a sigh of relief,” she told Israel Radio.

As if to underscore just how fragile the agreement would be, intense Palestinian rocket and mortar fire and Israeli air reprisals raged Wednesday. Shortly before the truce took hold, a Hamas militant was killed in an Israeli airstrike in central Gaza that the military said targeted a rocket squad.

Hamas, the Islamic militant group that has ruled Gaza for the past year, reported that the Israeli navy fired four shells into the waters off Gaza City minutes after the truce began. But the shells fell about 500 yards from shore and there were no apparent targets in the area, witnesses reported, suggesting the shells might have been fired as part of a military drill. The military said it had fired warning shots into the air after Palestinian fishermen entered Israeli waters.

Hours into the truce, there were no other reports of fire.

If the quiet holds, Israel will ease its blockade on Sunday to allow larger shipments of some supplies. A week later Israel is to further ease restrictions at cargo crossings, which in recent months have been closed to all but humanitarian aid and limited fuel supplies.

In a final stage, negotiators are to tackle Hamas’ demand to reopen a major border passage between Gaza and Egypt and Israel’s insistence that Hamas release an Israeli soldier it has held for two years.

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 coastal strip meant to quell rocket and mortar squads.

In an e-mail to reporters, Hamas’ military wing declared itself “completely and comprehensively” committed to the truce. But it warned that the cease-fire was not a “free gift to the occupiers” and said Hamas gunmen would launch a military strike if Israel did not abide by all its cease-fire commitments. “The ball is now in Israel’s court,” spokesman Sami Abu Zuhri said shortly before the truce went into effect.

The truce extends beyond Hamas to all militant groups operating in Gaza. Nafez Azzam of Islamic Jihad said the faction was “committed not to act against the interest of our people.”

Israeli government spokesman Mark Regev said Israel would “fully implement all its commitments” under the agreement, but said it would closely watch the other side.