Regional media earlier reported that the radical Islamic group, which controls the Gaza Strip, might favor the deployment of an Arab League peacekeeping contingent in Gaza in order to police cease-fire agreements between Palestinians and Israelis and between Fatah and Hamas rivals.
"We are strictly against such initiatives," Ismail Radwan said.
The Gaza Strip has been controlled by Hamas since June last year, leaving Palestinian President Mahmoud Abbas, who leads Fatah, in charge of only the West Bank. The two main Palestinian factions have been bitterly divided since then.
The situation in Gaza has sharply deteriorated following a mysterious bomb attack on Friday evening in which five Hamas members and a young girl died, Fatah-controlled media reported. Hamas blamed the attack on Fatah, which in turn denied responsibility.
The explosion went off under a car parked near a beach in Gaza City. Hamas said three of its members died on the spot along with a young girl, and that two other members were fatally wounded and died soon afterwards. More than a dozen bystanders were injured.
The media reports said the Hamas authorities in Gaza had carried out searches of more than 40 buildings containing Fatah offices on Saturday, arresting more than 170 Fatah activists.
Palestinian Fatah forces on Monday arrested at least 50 Hamas members throughout the West Bank in a tit-for-tat retaliation.
Radwan said Hamas would not agree on a Fatah proposal to carry out a joint investigation into Friday's explosion in Gaza.
"We will never accept this proposal," the Hamas spokesman said. "We have our own security structures and independent judges in whom we have a complete trust."
