Ms Kok, 44, of the Democratic Action Party (DAP), was arrested last Friday along with prominent blogger Raja Petra Kamaruddin, 57, and Chinese press journalist Tan Hoon Cheng, 33. The ISA allows for detention without trial.

Ms Tan's arrest triggered outrage even among government ministers, and she was released a day later. Raja Petra is still in police custody.

Ms Kok was detained for allegedly having petitioned several mosques in Selangor state to tone down the call to prayer, or azan, a charge she has denied. Two mosques have also dismissed the accusation.

Deputy Inspector-General of Police Ismail Omar said in a statement that the police had investigated Ms Kok for alleged involvement in matters considered to be a threat to national security.

'The police were satisfied with the cooperation extended by Teresa during the investigation,' he said. 'There was no reason to detain her further.'

The opposition MP described her arrest as a 'phenomenal abuse of the power of police under the ISA'.

At a press conference yesterday, she said: 'I do not know why I was released today, just as I do not know why I was detained.

'After being detained for seven days under the guise of so-called investigations, the police failed to produce any evidence or proof of me being involved in causing racial or religious tension.'

The government drew much flak for the arrests.

Observers and politicians - from the ruling coalition and opposition alike - slammed the move. The arrests also prompted one minister to resign.

Ms Tan, a journalist with Chinese-language newspaper Sin Chew Daily, had been arrested over an article in which she quoted an Umno chief as describing the Chinese as 'squatters'.

The comment sparked a row among component parties of the ruling coalition Barisan Nasional as well as within Umno, the coalition's biggest party.

Raja Petra was detained over a posting in which he allegedly attacked Islam.

Home Minister Syed Hamid Albar said Ms Kok was released not because police could not build up a case against her but because they were satisfied that she did not threaten national security, The Star reported.

'That was the principle behind her arrest and I believe that is also the reason why police have decided to release Kok,' he told reporters yesterday.

Ms Kok said that she had been made a scapegoat amid political squabbling within Umno.

She added that she would sue the Malay-language Utusan Malaysia daily for reporting her alleged involvement in the petition against the mosques, and sue the government over her arrest.

An Utusan reporter asked if she was willing to take a lie detector test to prove that she had no part in the azan controversy. Ms Kok said the test should first be used on her accusers, Malaysiakini reported yesterday.

She also said she was questioned on the allegations only twice - Saturday and Sunday - during her seven-day detention.

The only upsetting moment in her detention was when she was told her confinement would be extended by 28 days, she said.

'It was also ironic that the morning they arrested me, I was explaining to 300 businessmen from China that Malaysia was a politically stable country for them to do business with,' she said.

'Imagine their horror when the person who spoke to them on Friday appeared in the papers the next day, detained.'

As for her immediate plans, Ms Kok said that she would return to work as soon as possible.

Meanwhile, Raja Petra has applied for a habeas corpus - a legal action to produce a detainee in court and to justify his detention - in a bid to end his custody.

Yesterday, the High Court fixed to hear his application next Friday.

The blogger, who was previously charged with sedition and defamation after linking Deputy Prime Minister Najib Razak and his wife to a high-profile murder trial, filed a notice of motion describing his detention as unlawful and unconstitutional.

Another blogger who was arrested this week had his remand order extended for another day yesterday. Syed Azidi Syed Aziz, 38, was arrested under the Sedition Act after he urged Malaysians to fly the national flag upside down in protest against the government.

Meanwhile, two of the three newspapers which were issued warnings last week for breaching publication guidelines have handed in their show-cause letters.

Tan Sri Abdul Aziz bin Mohd Yusof, Secretary-General of the Home Affairs Ministry, said yesterday that the ministry had received letters from The Sun and Sin Chew Daily. But opposition party newsletter Suara Keadilan had not done so, Bernama reported.

The Sun was asked to show cause over unspecified articles on sensitive issues, while Sin Chew Daily's notice was over its report on the Umno politician's comment on the Chinese.

Suara Keadilan got into trouble for reporting that police chief Musa Hassan was paralysed after heart surgery.

In Washington, the US State Department reiterated that it viewed with 'grave concern' Malaysia's use of the ISA to stifle dissent.

hazlinh@sph.com.sg