A Hamas leader killed in his Dubai hotel room was drugged and then suffocated, police said on Sunday, giving further details of the Cold war-style hit allegedly carried out by Mossad agents.

Police also said that a Palestinian held in connection with the murder had helped the hit team with logistics.

"The killers used the drug succinylcholine to sedate (Mahmud) al-Mabhuh before they suffocated him," Major General Khamis Mattar al-Mazeina, deputy commander of Dubai police, said in a statement.

"The assassins used this method so that it would seem that his death was natural," Mazeina said, adding that "there were no signs of resistance shown by the victim."

Post-mortem test results revealed the presence of the drug, Mazeina said. He added that results did not indicate the amount injected, as the drug is difficult to trace.

Succinylcholine, also known as suxamethonium, is used to induce muscle relaxation and is favoured by anaesthetists and emergency doctors because of its fast onset.

It is "usually (used) for facilitation of endotracheal intubation" (inserting a tracheal tube), the statement quoted the General Department of Forensic Sciences and Criminology at Dubai Police as saying.

Mabhuh, one of the founders of Hamas' military wing, was found dead in his hotel room on January 20.

Israeli intelligence service Mossad has widely been accused of carrying out the assassination. Mabhuh is regarded by Israel as a key link in a weapons smuggling chain into Gaza, which is controlled by the Islamist movement Hamas.

Dubai police chief Dahi Khalfan has called on Meir Dagan, the head of Mossad, to come clean on the murder.

"Meir Dagan, the boss, should admit the crime... or present a categorical denial," government daily Emarat Al-Youm on Saturday quoted Khalfan as saying.

"But (Dagan's) current attitude shows he is afraid. Let him be a man, and tell the truth," Khalfan said.

Twelve British, six Irish, four French, one German and three Australian passports were used by the 26 people believed linked to the murder, according to Dubai police.

In many cases, the documents appeared either to have been faked or obtained illegally.

The issue has caused a diplomatic row in which the five countries whose passports were used have all called in Israeli envoys for talks.

Israel has sought to play down the row, saying there is no evidence of its involvement. It has rejected the calls for Dagan's arrest as "baseless" and "absurd."

In addition to the 26 Western suspects, police have announced that they have two Palestinians in custody, both residents of the emirate who had fled but were extradited back from Jordan.

The Dubai police chief on Sunday told Al-Arabiya news channel that one of the Palestinian suspects had allegedly provided "logistics assistance" to the hit squad.

The Dubai police "alone and without any outside help" was able to re-enact the murder, Khalfan added.

Al-Ittihad newspaper reported last week that a third Palestinian was also being held for questioning but there has been no official confirmation of that report.