The Egyptian government has begun sealing a series of smugglers’ tunnels between its border and the Gaza Strip, witnesses and security officials said Sunday, in an apparent attempt to increase security after a violent cross-border incident with Israel set off the worst diplomatic conflict between the countries since the Camp David Accords.

The area around the town of Rafah is rife with smuggling, as hundreds of tunnels ferry construction materials, consumer goods and weapons into Gaza to bypass the Israeli blockade. Israel contends the tunnels also facilitate attacks by militants.

The smuggling has only increased since the ouster of former Egyptian president Hosni Mubarak in February, as police officers pulled back from the Sinai Peninsula in the early days of the uprising, decreasing security in the area.

Then on Aug. 18, militants, who Israel said had criss-crossed from Gaza into Egypt and back again, attacked an Israeli resort town, killing eight. Israeli security forces killed five Egyptian border guards in the crossfire as they pursued the attackers. Since then, a new resolve to secure the region has set in on both sides of the border.

The Egyptian military “brought their stones and their concrete,” using large equipment to destroy tunnels, in some cases filling them with concrete and gravel, said Fathy al-Nahas, 40, a contractor who owns a small tunnel near the border with Gaza, in a telephone interview Sunday. He said that he used his tunnel — which he said was too narrow to fit a person — to send building supplies into Gaza.

The action was a sign that Egypt remained too close to Israel, he said. “The government won’t upset Israel or America.”

Thousands of Egyptian troops have fanned into Sinai over the last month as Egypt has attempted to increase security. The heightened troop presence is yet another sign of the new relationship taking shape between Israel and Egypt, after decades in which Mubarak’s tolerant if unenthusiastic stance toward Israel was far more conciliatory than Egyptian public opinion.

The Camp David Accords, the historic peace accord between Egypt and Israel signed in 1978, limit the number of Egyptian troops that can be stationed in Sinai. In May, Egypt reopened the Rafah border crossing into Gaza, after closing it in cooperation with Israel when Hamas took over the administration of Gaza in 2007. The crossing is the only official entry point outside Israel into Gaza.

But with the reopening of the overland border, Egypt now is apparently seeking to cut off the underground border. It has closed tunnels in the past , but they have quickly reappeared.

The Associated Press quoted unnamed Egyptian security officials as saying that they were seeking to close the tunnels and had started to do so on Wednesday. Three main tunnels have been found, the officials said, and one has been closed so far.

Last week, contractors in Cairo began constructing a 10-foot concrete wall around the residential building that houses the Israeli Embassy, after crowds of hundreds and sometimes thousands had gathered to protest against the Israeli government in the weeks since the border incident.

Hassieb is a special correspondent.