BEIRUT: Four security chiefs detained in the assassination of former Lebanese Prime Minister Rafik Hariri were last night charged "with murder, attempted murder and carrying out a terrorist act."

Chief Investigating Magistrate Saeid Mirza formally charged the suspects after extending their detention for an extra 48 hours. The suspects, Major General Jamil Sayyed, the former head of General Security, Major General Ali Hajj, the former director general of the Internal Security Forces, Brigadier General Raymond Azar, the former director general of military intelligence, and Brigadier General Mustafa Hamdan, commander of Lebanon's Presidential Guards, have already spent three days in custody and will now be interrogated by Investigating Judge Elias Eid later today.

The latest move came just hours after Detlev Mehlis, the head of UN international probe into the assassination, said more detentions were imminent.

Speaking during a news conference Mehlis said: "In our assessment, the five suspects we have are only part of the picture. We will have to further investigate and we do think more people are involved."

Mehlis added that he "suggested" to the Lebanese judiciary that the four should be formally arrested.

He said: "We think they were, to some extent, part of the planning of the assassination. If it is so then it has to be determined. We are still working on the motive."

Mehlis added he will extend the fixed time length of the investigation. He said: "We will not be able to finish our work by September 15, the set deadline."

Mehlis said that "so far" there were no Syrian suspects in the case. Syria, which has been accused of the murder by a number of Lebanese politicians, has been criticised by the UN for failing to fully cooperate with the investigation.

Mehlis said he "has asked to interview those Syrian representatives who were at some point responsible for security in Lebanon."

But added: "We have faced some delay because of lack of cooperation. But if the Syrians don't cooperate, what can I do? Nothing."

Mehlis also said that there was "no indication that Hizbullah has any part in the crime whatsoever," quelling speculation that the Lebanese resistance group, currently under international pressure to disarm, was going to be named as a suspect.

After Mehlis' comments U.S. Ambassador to Lebanon, Jeffrey Feltman said: "We understood that Mehlis has asked for full cooperation from the Syrians. We wish the Syrians would reply to his requests, because we think it is important."

Lebanon's President Emile Lahoud, who has come under increasing pressure to stand down following the initial detention of his close aide Hamdan, urged the investigation to "identify those who masterminded and committed the heinous crime."

Mehlis, who stressed the president was "not a suspect" said he he had met with Lahoud several times "but not after the arrests took place."

Meanwhile, MP Saad Hariri criticized Lahoud's earlier defense of Hamdan. Lahoud said that Hamdan "is a distinguished officer" and insisted he was innocent until proven otherwise.

Speaking form Paris, Hariri warned against "attempts to surpass the course of investigation" from what he called "official parties who are in a suspicious position."

Press Adviser of the Lebanese Presidency Rafik Shlala insisted Lahoud will not step down. He said: "The president would stay in his office and assume his national responsibilities that are stated by the Lebanese Constitution."

Mehlis has also revealed that the probe has "no knowledge of a hit list." A number of Lebanese politicians abruptly left for Paris last week after some said they had been warned by officials of threats to their lives.

Mehlis said: "I haven't seen a hit list, and if it is true we will inform the Lebanese authorities because we are not in a position to advise people on their security."

Meanwhile, ISF personnel raided another apartment in Mouawad Street in Beirut's southern suburbs. The move comes after the ISF raided the wrong apartment in Mouawad Street on Wednesday along with other apartments in Naameh and Khaldeh and detained three people. The three were later released after the probe found no connection between them and the crime. Mehlis apologized for the mistake.