Thursday, July 28 2005 11:02 Hrs (IST) - World Time -

London: In a major breakthrough in the investigation of the failed July 21 attacks in London, British police yesterday (July 27, 2005) arrested Somali-born Yasin Hassan Omar, one of the four suspects, during pre-dawn raids in central city of Birmingham.

Omar, 24, suspected of an attack near Warren Street Tube Station, was held in raids in his brown-brick duplex after being stunned with a taser gun, police said.

"I can confirm that one of the men that has been arrested in Birmingham is Yasin Hassan Omar, he was alone in the house at the time of his arrest," Peter Clarke, head of London Police's Anti-Terrorist branch told reporters.

Police had earlier released photographs of all four July 21 suspected bombers and identified two Omar and 27-year-old Muktar Said Ibrahim.

Clarke confirmed that Hassan Omar was subdued with a stun gun but no traces of explosives were found at the house in Heybarnes Road, east of Birmingham, on which raids were conducted before dawn.

"A detailed forensic examination is taking place it will take some time to complete. This is of course an important development in out investigation," Clarke said.

He emphasised that the three other suspects still remain a threat.

Hassan Omar is now being held at a London police station for interrogation, he said.

Shortly after his arrest at Heybarnes Road three more men were arrested in a raid at a second home in Bankdale Road, also in east Birmingham.

Immigration officials had disclosed that Ibrahim and another Omar came to Britain as child refugees. Omar came from Somalia as a 10-year-old in 1992 while Ibrahim arrived with his parents the same year from Eritrea, aged 14.

In another development, British police yesterday freed without charge two men who had been detained under anti-terrorism laws at a train station in northeast England.

The pair was arrested yesterday at Grantham railway station under the Terrorism Act as they traveled from Newcastle to Kings Cross station in London, Lincolnshire.

Police had said earlier that they were detained under the Prevention of Terrorism Act.

But later it amended its statement saying "Following extensive inquiries yesterday we are now satisfied that the men arrested from the train at Grantham last night are not connected to any terrorist activity."

"They have been released from our custody without any charge and the matter is now closed," a Lincolnshire Police spokesman said.

Prime Minister Tony Blair has described the arrest as an 'important development,' and said "The arrests raised hopes that a key suspect is now in custody."