A Palestinian family sit next to their destroyed home in the area of east Jebaliya in the northern Gaza Strip on Wednesday. (Bernat Armangue/Associated Press)A rocket fired from the Gaza Strip struck southern Israel on Wednesday, further straining a fragile 10-day-old ceasefire just hours after Israeli warplanes bombed smuggling tunnels along the Palestinian territory's border with Egypt.

The rocket attack is the first of its kind since the truce on Jan. 18 ended Israel's three-week offensive against militant group Hamas in the coastal enclave.

An Israeli military spokesman said there were no injuries or damages caused by the rocket attack.

Meanwhile, during a visit to the region Wednesday, U.S. President Barack Obama's new Mideast envoy said Gaza militants must end weapons smuggling and the territory's blockaded borders must be fully opened if the ceasefire is to last.

The Israeli air strikes come a day after an Israeli soldier was killed and three others injured in a roadside bomb explosion along the Israeli-Gaza border.

Shortly after the deadly explosion, Israel sent tanks and bulldozers into northern Gaza to plow up the attack site and launched an air strike that wounded a Hamas militant "who was prominent in the organization accountable for the attack," the military said.

Hamas said the Israeli strike injured one of its men as he rode a motorcycle in the southern Gaza town of Khan Younis.

Reuters reported a little-known Islamist group has claimed responsibility for the attack on the Israeli soldiers, but the news agency didn't give the group's name.

Reflecting the seriousness of the situation, Israeli Defence Minister Ehud Barak cancelled a planned trip to Washington this week to stay home and deal with the crisis, defence officials said.

The violence has rattled the shaky calm between Israel and Hamas, the Palestinian militant group that controls the Gaza Strip. Each side separately declared a ceasefire on Jan. 18 following a 22-day campaign of Israeli air strikes and Palestinian rocket attacks.

The offensive has killed 1,285 Palestinians, more than half of them civilians, according to records kept by the Palestinian Centre for Human Rights. Thirteen Israelis, including three civilians, were also killed during the fighting.

Ceasefires must be consolidated: envoy

Israeli Prime Minister Ehud Olmert, right, meets with U.S. Middle East envoy, George Mitchell, centre, in Jerusalem on Wednesday. (Matty Stern/Associated Press)Obama, who has pledged to listen to all sides in the conflict, sent U.S. Mideast envoy George Mitchell on an eight-day visit to meet with leaders in the region and bolster the ceasefire.

"It is of critical importance that the ceasefire be extended and consolidated, and we support Egypt's continuing efforts in that regard," Mitchell said after talks in Jerusalem with Israeli Prime Minister Ehud Olmert.

"The United States is committed to vigorously pursuing lasting peace and stability in the region," Mitchell said, adding that his visit, which comes so soon after Obama's inauguration last week, "is clear and tangible evidence to this commitment."

Mitchell, a former U.S. senator, helped resolve the conflict in Northern Ireland and headed a commission that made Israeli-Palestinian peace recommendations in 2001.

He will also meet with Palestinian President Mahmoud Abbas in the West Bank. Mitchell will not meet with representatives of Hamas.

At his West Bank headquarters, Abbas said Tuesday he was looking forward to working with the new U.S. administration.

With files from the Associated Press