The Islamist group Hamas said on Monday Egypt was responsible for the deaths of eight Palestinians because it used water, gas and explosives to seal a network of tunnels under its border with the Gaza Strip.
Hamas Interior Ministry spokesman Ehab al-Ghsain criticised Egypt's tactics as dangerous. Three Palestinians were crushed to death on Monday when their tunnel under the border collapsed, medics said. Five others suffocated on Aug 1.
Palestinians have dug dozens of tunnels to ease Israeli blockade over the Gaza Strip.
Ghsain said Cairo shares the blame with Israel for the blockade by keeping the coastal enclave's only border crossing with Egypt closed.
"We understand the American and Israeli pressure on Egypt but that does not justify the killing of people in such a manner," Ghsain said.
He defended Gaza's tunnel network, saying it was a result of the blockade.
"Once the Rafah crossing opens and the blockade is lifted, the tunnel issue will be resolved," he said.
Egyptian security sources confirmed that Egypt had pumped gas into tunnels in recent months before sealing them off.
They said the gas was not harmful and was used to prevent Palestinians from trying to re-enter the tunnels.
The sources said Egyptian authorities "typically informed their Palestinian counterparts" once the tunnels were sealed.
Egypt's Interior Ministry had no immediate comment.
The United States and Israel have pressed Egypt to seal the tunnels. U.S. experts have been cooperating Egyptian security forces look for tunnels.