A ceasefire between Israel and Hamas has begun in the Gaza Strip - but both sides have voiced doubt over how long it will hold.

The Egyptian-brokered truce began at 6am after another day of cross-border violence.

Medical workers and militants said just before it came into effect, an Israeli missile strike killed one Palestinian gunman and wounded another near the border fence with Israel in the central part of the Gaza Strip.

Israeli Prime Minister Ehud Olmert said. "What they are calling a 'calm' is fragile and likely to be short-lived.

"Hamas and other terrorist groups have not changed their stripes or turned into lovers of peace," he said, reiterating a threat to invade Gaza should the truce collapse.

Meanwhile, Hamas's Izz El-Deen al-Qassam Brigade, the Islamist group's armed wing, said in a statement that the ceasefire was "not in anyway a free gift" to Israel and warned against any violations by the Jewish state.

"Qassam Brigades is fully ready to launch a military strike that would shake the Zionist entity if they did not abide by all the items of the calm deal and the Zionist enemy would be responsible for any foolish act they may commit," the statement said.

Western officials said Israel planned to allow in a slightly higher number of truckloads of goods starting on Sunday, provided the truce was still in place. The Palestinians have demanded the full flow of imports restored.

Hamas leader Ismail Haniyeh voiced confidence all factions would respect Thursday's deal out of a sense of "national responsibility".

But the faction's armed wing has made clear it would not stop training and arming its fighters and was ready to resume attacks.

Spokesman Abu Ubaida said: "We have no illusions that the Occupation (Israel) has good intentions toward our people, and should the Occupation foil the calm, it would mean a return to an even stronger resistance."

Hamas rules Gaza but smaller Palestinian armed groups have in the past defied its ceasefire calls. The most recent Gaza truce, in November 2006, broke down quickly.

The latest deal does not cover the occupied West Bank, where Mr Abbas holds sway and where Israeli troops regularly operate. Bloodshed there could potentially trigger reprisals from Gaza.

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