KUALA LUMPUR, Malaysia (Reuters) - Malaysian authorities Wednesday tightened a legal noose around sacked finance minister Anwar Ibrahim as a top aide appeared before police investigators in the sex-and-treason case.

Anwar's private secretary, Mohamed Azmin Ali, went to federal police headquarters in the capital early Wednesday accompanied by two lawyers, witnesses said.

Azmin, who had initially balked at coming forward, told reporters as he left Anwar's suburban home that police had asked him to come in for questioning in connection with the probe.

Police have confirmed that Anwar's former Finance Ministry secretary and a former speechwriter had been detained earlier this week over an investigation into alleged crimes by Anwar.

Police Monday had arrested Munawar Anees, a Pakistani national with permanent resident status in Malaysia.

Anwar said Munawar had been detained under the Internal Security Act (ISA), which allows detention without charges. Munawar had worked for a local publishing company and written speeches for Anwar, aides to the former minister said.

Police also arrested Anwar's former private secretary at the Finance Ministry, Mohamad Ahmad, Tuesday.

They were the third and fourth arrests in connection with allegations of sexual misconduct, treason and corruption aimed at Anwar.

Last month police arrested a businessman friend of Anwar's under the ISA. Anwar said last week that his adopted brother had also been arrested.

Anwar likened the police action in arresting his former aides and friends as those of the Israeli intelligence services.

``His (Mohamad) family members were warned not to inform anybody -- his lawyer, me, or any member of my team. I don't know what kind of system (they are operating under) -- the Shabak or Mossad?'' the New Straits Times newspaper Wednesday quoted Anwar as telling reporters.

Federal police chief Abdul Rahim Mohamad Noor said Wednesday Anwar's remarks were most unacceptable.

``If it was indeed true that Anwar has likened the police investigations to that in Israel, the police just feel so uncomfortable as the word Israel is regarded as extremely sensitive by the people and in the country,'' the official Bernama news agency quoted Abdul Rahim as saying.

``If Anwar has stated that the police are using the law of the jungle in investigating allegations against him, I can understand that, considering the mental state he is in at the moment,'' he said.

The police inspector-general said saying late Tuesday that Anwar would be arrested if he continued to hold public assemblies without a permit.

``If there is no permit he cannot (hold assemblies),'' Abdul Rahim said. ``As a former cabinet member, he should know the law.''

Anwar, who was sacked on September 2 and expelled from his political party one day later, has been holding meetings at his suburban home in Kuala Lumpur which have drawn thousands of people. Police have not intervened although permits have not been granted.

Anwar said Tuesday that he expected to be arrested after the Commonwealth Games, which end next Monday.

The former heir-apparent to Prime Minister Mahathir Mohamad told reporters that the arrests were part of a campaign to incriminate him and foreshadowed his own arrest.

``They will wait until Her Majesty the Queen leaves, and they will probably do what is necessary,'' he said.

Britain's Queen Elizabeth was scheduled to arrive in Kuala Lumpur Sunday and stay until September 23.