Egypt launched air strikes near its border with Israel on Wednesday and killed more than 20 suspected Islamic militants, in a crackdown on jihadists blamed for a deadly attack on Egyptian border police, an army official and eyewitnesses said.
The air strikes around the town of Sheikh Zuwaid, 10 kilometres from the Gaza Strip, followed clashes overnight between armed men and security forces at several checkpoints in the north of Egypt's Sinai region.
Gunmen killed 16 border guards on Sunday in the bloodiest attack on security forces in the tense Sinai region in decades. They seized two armoured vehicles to storm through the border into Israel, where they were eventually killed by Israeli fire.
Israel said Egypt's military action was a necessary response to deal with groups threatening security along the isolated desert frontier.
Witnesses in the town said they saw two military planes fly over the area and heard explosions. Other people near the town said they saw three cars bombed.
Troops entered the village of al-Toumah close to Sheikh Zuwaid as part of the operation after the army received information that Islamist militants were staying there, a military commander in Sinai told Reuters.
"We have succeeded in entering al-Toumah village, killed 20 terrorists and destroyed three armoured cars belonging to terrorists. Operations are still ongoing," he said by telephone.
Israel stepped up pressure on Egypt's government to get a grip on lawlessless near the border. Egypt's army promised harsh retribution for the attackers, branding them "infidels".
There was little sign of an immediate crackdown by Egyptian security forces until Tuesday night when armed men opened fire on several checkpoints in al-Arish town, the main state security and administrative centre for northern Sinai.
Gunmen also attacked checkpoints in Rafah, Egypt's entry point into the Palestinian-controlled Gaza Strip that borders both Israel and Egypt.
A statement issued by the interior ministry said three policemen and one resident were wounded in those assaults.
The military response focused immediately on Shaikh Zuwaid, a town that has come under the control by Bedouin tribesmen as the authorities lost their hold over swathes of northern Sinai following the overthrow last year of president Hosni Mubarak.
The economically deprived town has come to rely heavily on profits from smuggling goods and people through tunnels into Gaza since the Palestinian territory was cut off from Israel.
In al-Arish, a town relatively developed compared to others in the region, residents poured onto the streets overnight to demand better protection from the government and arms to defend themselves after the armed men attacked the town's checkpoints.
One of the checkpoints targeted on Wednesday had been attacked 28 times b efore s ince the uprising, the Egyptian state news agency MENA reported.
Security forces closed Arish's main highway shortly after the start of the military operation. Power, Internet and mobile phone networks in the area were shut down.
The Egyptian army's operation appeared to be one of the biggest in the area since it signed a peace treaty with Israel in 1979 that put strict limits on troop movements in Sinai.
Israel says it has agreed in the past to Egyptian requests to bring more troops into Sinai and the terms of the treaty are no obstacle to combating militants threatening both countries.
"What we see in Egypt is a strong fury, a determination of the regime and the army to take care of it and impose order in Sinai because that is their responsibility," senior Israeli defense official Amos Gilad said on Israel Radio on Wednesday.
"This is an Egyptian action that is being handled by the Egyptians on the basis of the information they have," he said. "If they don't remove and uproot (the threat), it will continue to strike."
Earlier on Tuesday, angry mourners wept at the military funeral in Cairo of the border guards slain on Sunday and Egypt began to seal off the smuggling tunnels into Gaza, according to another security source and an eyewitness.
Mr. Mubarak's government worked closely with Israel to secure the frontier region until he was toppled in a popular uprising 18 months ago.
The revolt made way for Egypt's first free leadership vote which brought into office an Islamist whose commitment to security co-operation with the Jewish state has yet to be tested.