CAIRO – The Egyptian government has begun sealing a series of tunnels between its border and the Gaza Strip, witnesses and security officials said Sunday, in an 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.

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 the 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. He said that he used his tunnel to send building supplies into Gaza.

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

Thousands of Egyptian troops have fanned into Sinai in the last month in 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 agreement 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 when Hamas took over the administration of Gaza in 2007. The crossing is the only official entry point outside Israel into Gaza.