The stabbing death of a detective in an anti-terrorism sweep raised questions about how well British police are equipped to deal with terror suspects: the arrested men had not been restrained and some of the police were unarmed and wore no body armor.

Police launched an internal inquiry Wednesday into the botched raid after criticism from lawmakers and fellow officers that the operation was badly planned and under-equipped.

Detective constable Stephen Oake, 40, was killed and four other officers were injured Tuesday during the raid on an apartment in the northern city of Manchester. Police were searching for a suspect in the Jan. 5 discovery of the deadly poison ricin in London.

Three North African men were under arrest Wednesday under anti-terrorism laws -- one being questioned about the ricin, another about Oake's death, and the third was being handed over to immigration authorities.

Prime Minister Tony Blair, who described Oake's death as a "wicked murder," stressed the need to "redouble" efforts in the fight against terrorism but did not comment on the way the raid was conducted.

But Norman Brennan, a police officer and director of the action group Victims of Crime Trust, said the killing showed that officers need more protection.

British police usually don't carry guns, though in cities they sometimes wear protective clothing.

"Police officers only have the protection that the government wants them to have at the moment, and it's not enough," Brennan said.

Opposition politicians said the government needed tougher measures to screen asylum seekers for possible terrorist suspects, and also criticized the apparent blunders in police operations.

Police going into the raid were ill-prepared from the start, according to media reports: The officers were told to be ready for one suspect but instead found three. The officers also were reportedly told not to expect a struggle.

Still, the Manchester force defended its decision not to equip all the 24 officers taking part in the raid with body armor.

Armed police entered the apartment first and detained the three suspects. Then, Oake and other officers of the intelligence-gathering Special Branch began forensic examinations on the suspects, which made it difficult to restrain them.

"There was no perceived risk," said Manchester police chief Michael Todd. The suspects "were detained and actually being held by officers at the time. So it was then decided that you can't handcuff someone while you are actually conducting that sort of (forensic) examination."

One suspect broke free from the hold of an unarmed officer and a tussle followed. The suspect grabbed a kitchen knife. Oake was stabbed as he went to assist his colleagues, Todd said.

"We will be looking into the lessons which can be learned from this," he added.

Oliver Letwin, law and order spokesman for the main opposition Conservatives, said the raid "clearly went badly wrong in some respects."

Letwin also said there was "ample evidence" that asylum seekers were getting into Britain with intent to pursue terrorist activities.

Home Secretary David Blunkett rejected that criticism, saying the raid showed that safeguards against terrorism were in place but needed to be further refined. "We are on top of those who threaten our lives and livelihoods," he said.

British authorities have been warning for months that the country faces a serious threat of terrorist attack; Blair said finding ricin in London highlighted the dangers Britain faces.

Derived from the castor bean plant, ricin is one of the world's deadliest toxins and has been linked in the past to Usama bin Laden's Al Qaeda terror network and Iraq.

In the London ricin case, four men described as North African appeared in court Monday charged with chemical weapons and terrorism offenses.

Manchester police said they found no traces of ricin in Tuesday's raid. On Wednesday, more police began a search of surrounding apartments -- this time wearing camouflage suits and gas masks and some carrying riot shields.

A police spokeswoman said the officers were making sure it was safe for forensic experts to continue their investigation.