Egyptian security forces killed six gunmen in a raid on a village of North Sinai on Sunday, witnesses said, as the military pressed a campaign against Islamists in the lawless peninsula neighbouring Gaza and Israel.
Security officials said they found chemicals used to make explosives, rocket-propelled grenades and machineguns with the militants in El-Jurah village. One of the gunmen was seriously wounded, they said.
The bodies of three gunmen were charred in a fire that broke out during an exchange of gunfire, in which the soldiers fired at the house with machineguns mounted on armoured personnel carriers.
The cause of the blaze was unclear but witnesses said they did not see any air strikes.
"The security forces raided a small house in the village, and there was an exchange of gunfire," said one witness, who requested anonymity.
"They killed six people and left the bodies, and came back with ambulances and a fire truck to retrieve them," he said.
Another witness, who described the gunmen as "strangers" to the village, said the six men were killed when security forces entered a home they were hiding in.
Witnesses said no troops appeared to have been killed in the raid.
Earlier, however, three soldiers died in a road accident elsewhere in the peninsula as troops fanned out to secure checkpoints and massed near the borders with the Gaza Strip and Israel.
Overnight, gunmen traded fire with security forces at a checkpoint in the town of Sheikh Zuwayid, several kilometres (miles) from El-Jurah, security officials said. No casualties were reported in the clash.
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Sunday's raid came as the military sent more tanks and armoured vehicles to Sinai in an unprecedented campaign to capture or kill Islamic militants behind an attack on an army outpost that killed 16 soldiers on August 5.
It claimed to have killed 20 militants in Wednesday's air strikes, but witnesses said there were no deaths in the helicopter attacks, the first in the Sinai in decades.
Official media reported on Friday that security forces arrested six "terrorists" in the town of Sheikh Zuwayid, 15 kilometres (nine miles) from the border with Gaza.
Their relatives told AFP that nine men were arrested, some of them relatives and all devout Muslims. They had nothing to do with the attack on the soldiers, and they were asleep in their homes when masked security forces burst in on them.
Hazem Yusef, a relative of several of the arrested men, said on Sunday three of them have been released, leaving six in detention.
The military campaign has seen the largest buildup of troops in the Sinai since Israel returned the territory under a 1979 peace treaty that restricted Egypt's military presence on the peninsula.
The Egyptian military believes Islamist Bedouin militants work with radical extremists in Gaza.
The Islamist movement Hamas which rules Gaza insisted on Sunday there was no proof to date of any Palestinian involvement in the attack on the Egyptian military.
"Until now, neither the Palestinian nor the Egyptian security services have proof that any party in Gaza supported or executed the attack," said senior Hamas official Salah al-Bardawil.
"Egypt hasn't supplied the Gaza government with any accusation or given any information about the involvement of Palestinians," he told reporters. "If it is proven that a Palestinian was involved, then measures will be taken."
Within hours of the attack, sources in Cairo suggested some of the gunmen had entered Sinai through a network of smuggling tunnels which run under the Gaza border, prompting Hamas to take the unprecedented step of shutting them down.