An explosion in the southern Gaza Strip killed four Palestinians on Saturday, the local health ministry said.
Medics at the scene in the Rafah area said it was caused by an Israeli tank shell.
But an Israeli military spokesman said the army was not involved. "We have no knowledge of any Israeli strike in the area," he said.
Local residents at the hospital morgue identified the four dead men as members of the Palestinian Islamic Jihad militant group. Islamic Jihad did not immediately confirm the men were members.
Violence has flared in the Gaza Strip since March 30, when Palestinians began protests along the border area with Israel.
Israeli troops have shot dead 31 Gaza Palestinians and wounded hundreds since the protests began, drawing international criticism of their lethal tactics.
Protesters have set up tented camps near the frontier as a protest dubbed The Great March of Return - evoking a longtime call for refugees to regain ancestral homes in what is now Israel - moved into its third week.
Israel has declared a no-go zone close to the Gaza border fence.
Israel withdrew its troops and settlers from Gaza in 2005. The Palestinian enclave is ruled by the Islamist Hamas movement, designated by Israel and the West as a terrorist group.
Citing security concerns, Israel maintains a naval blockade of the coastal territory, keeping tight restrictions on the movement of Palestinians and goods across the frontier.
Egypt, battling an Islamist insurgency in neighboring Sinai, keeps its border with Gaza largely closed.