Palestinian medical workers say a member of a militant group has died in an explosion in the Gaza Strip.
Another militant is said to have been seriously injured in the incident, which happened near a refugee camp.
Witnesses say the blast was caused by an Israeli air attack, but the Israeli army has denied involvement.
The incident comes a day after aid agencies warned of a humanitarian catastrophe in Gaza if a five-month-old ceasefire is allowed to collapse.
The Popular Resistance Committees militant group said that an Israeli air strike had targeted a group of its fighters as they approached the Israel-Gaza border near the northern town of Beit Hanoun.
However, a spokesman for the Israeli army denied that it had carried out an air strike.
Analysts say the conflicting reports highlight growing tensions between Israel and the Palestinians as the five-month-old Gaza truce continues to unravel.
