Egypt began work to seal off smuggling tunnels into the Gaza Strip on Tuesday, a security source said, two days after gunmen shot dead 16 Egyptian border guards in an attack blamed partly on Palestinian jihadi militants.
A Reuters reporter in the border town of Rafah said heavy equipment was brought to the Egyptian side of the tunnels, which are used to smuggle people to and from Gaza, but also food and fuel that are a lifeline for the small territory's population.
"The campaign aims at closing all the openings between Egypt and the Gaza Strip that are used in smuggling operations," said the security source.
New Egyptian President Mohamed Morsi quickly pledged to bring the region back under government control after the attack on Sunday, the worst since Egypt made peace with Israel in 1979, ending a succession of wars.
Egyptian security forces began arresting suspects in the main northern Sinai town of al-Arish on Tuesday, the security source said, and officials checked names of potential suspects who were released from prison since Mubarak was ousted.
But there was little visible sign of a troop build-up in the area and people in Sinai said security at checkpoints on a main road into northern Sinai was no greater than normal.
Officials said they were still planning their next move.
"Extensive meetings are currently taking place between top officials in the army, interior ministry and border guard to come up with a plan to detect and find the criminals behind Sunday's attacks," a second security source said.
Another said the absence of a quick increase in security might lure the militants behind the attack into an attempt to flee the area, and "they would then be caught by the police."
Meanwhile, Hamas condemned the killings of the Egyptians and said it was sealing the tunnels from its side while helping Egypt to identify those behind the attack.
As officials weighed how to strike back after the deadliest assault along Egypt's tense Sinai Peninsula frontier with Israel and Gaza in decades, crowds of angry mourners wept at the military funeral for the slain guards in Cairo.
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