"There were seven or more people holding passports from different European countries" in the group suspected of killing Mabhuh, he said.
Khalfan refused to name the countries, but added, "we are currently in contact with these European countries to verify the authenticity of the passports."
The hardline Hamas on Friday accused Israel of killing Mabhuh, who was found dead in his hotel room in Dubai on January 20, and vowed revenge.
Hamas has acknowledged that Mabhuh was in Dubai to buy weapons for Hamas in its struggle against Israel's occupation of Palestinian territories.
Mabhuh's brother Fayeq told AFP he had been targeted in the past.
Several months ago the 50-year-old father of four was taken in a coma to a hospital in Damascus where he had been based for years. Doctors later told him he had been poisoned.
Mabhuh, born in Jabaliya in northern Gaza, was behind the capture of two Israeli soldiers, Avi Sasportas and Ilan Sadon, in separate operations in 1989. Both were later murdered.
Khalfan said that "it seems (Mabhuh) opened the door" of his room, letting his killers in. "Mabhuh was suffocated," he said, adding that "strangulation is possible."
According to Khalfan, Mabhuh entered the United Arab Emirates (UAE) a day before his death using a passport that did not bear his family name.
"We were not informed by Hamas about the visit," he said. "It is strange that a person of his importance travelled alone."
Khalfan met Palestinian consul general Hussein Abdul Khaliq in Dubai on Sunday to discuss the murder, saying police would "work day and night" to track down the suspects, the official WAM news agency reported.
Israeli newspapers, meanwhile, hailed the killing, with the rightwing Jerusalem Post calling it "another blow to the 'axis of evil'" that will make it harder for Hamas to get arms into its Gaza stronghold.
Britain's The Sunday Times newspaper cited unidentified Middle Eastern sources as saying Mabhuh's body was found by staff at the luxury Al Bustan Rotana hotel.
It said Mabhuh was travelling on a false passport and on arrival in Dubai was followed by two men described by local police as "Europeans carrying European passports."
The Sunday Times said the hit squad injected Mabhuh with a drug that induced a heart attack, photographed all the documents in his briefcase, and left a "do not disturb" sign on the door.
It added that the Hamas leader was on a mission to buy arms from Iran, and was tracked from the moment he boarded Emirates flight EK 912 from Damascus on January 18.
A founder of Hamas' military wing, Mabhuh was in charge of arms purchases for the group.
Over the years, a number of Hamas leaders have died in what Israel calls "targeted killings."
In 2004, Hamas founder Sheikh Ahmed Yassin was killed in an Israeli helicopter gunship attack in Gaza. One month later, another Hamas leader in the enclave, Abdel Aziz al-Rantissi, was killed when two missiles hit his car.
In 1997, Israeli agents tried to poison Hamas leader Khaled Meshaal in Amman, while in 1995, Mossad succeeded in killing Islamic Jihad chief Fathi Shiqaqi in Malta.
In 1988, Israeli commandos killed Abu Jihad, Yasser Arafat's right-hand man, in Tunis.
And in 1973, commandos, among them future prime minister and current defence minister Ehud Barak, killed three Palestine Liberation Organisation leaders in Beirut.
Dubai, a rich and glitzy city-state in the UAE federation, has exposed its murkier side with several high-profile murders in recent years.
Sulim Yamadayev, a bitter foe of pro-Russia Chechen leader Ramzan Kadyrov, was shot dead here last March, and Lebanese singer Suzanne Tamim was found dead in her Dubai home in July 2008. She had been stabbed and her face mutilated.
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