CAIRO (Reuters) - Egyptian police arrested a cousin of late Libyan dictator Muammar Gaddafi, a former Libyan ambassador to Egypt and another ex-Libyan official on Tuesday, a security source told Reuters.

The source said Ahmed Gaddaf Alddam, 60, a Gaddafi relative who had been a special Libyan envoy, former ambassador Ali Maria and Mohamed Ibrahim Mansour, who headed a Libyan state fund under Gaddafi, were all detained.

Interpol's website said Gaddaf Alddam was wanted by Libyan authorities for alleged counterfeiting, forgery, fraud and money laundering, and that Mansour was wanted for alleged corruption. Details on charges against Ali Maria were not immediately available.

An aide to the Egyptian prosecutor general said he had ordered that Gaddaf Alddam, Ali Maria and Mansour be detained for 30 days pending the arrival of paperwork from Libya needed for extradition.

Police surrounded Gaddaf Alddam's apartment during his arrest, the security source said.

In Tripoli, Libyan Prime Minister Ali Zeidan welcomed news of the arrests and called for the immediate handover of the men.

He said Ali al-Kilani, a former military general under Gaddafi who was in charge of television and radio stations in Libya, had also been arrested in Egypt.

"They will face a fair trial here," Zeidan told a news conference.

"They will be detained under conditions that meet international standards," he said, citing the example of other former Gaddafi officials currently in jail in the Libyan capital, including ex-spy chief Abdullah al-Senussi and former Prime Minister Al Baghdadi al-Mahmoudi.

Libya's new rulers, who aim to draw up a democratic constitution this year, are keen to try Gaddafi's family members and loyalists at home to show citizens that those who helped Gaddafi stay in power for 42 years are being punished.

Human rights activists worry a weak central government and a relative lack of rule of law mean legal proceedings will not meet international standards.

Gaddafi was overthrown and killed in an armed uprising in 2011.

(Reporting by Asma Alsharif; Additional reporting by Ali Shuaib in Tripoli; Editing by Mark Heinrich and Pravin Char)