LONDON and ROTTERDAM (AP) – Anti-terrorist officers arrested nine men in dawn raids on Thursday in connection with the botched July 21 attacks on London”s transit system.

Scotland Yard police headquarters said the men were arrested under the Terrorism Act at two properties in the neighborhood of Tooting, south London. They were being held in a central London police station.

The arrests follow a significant breakthrough on Wednesday, when police officers arrested in Birmingham, central England, one of the four men suspected of carrying out the failed attacks, Yasin Hassan Omar, 24. He was being held at a top-security police station in London.

The three other bombers suspected of carrying out last week”s attacks were still on the run and not among Thursday”s arrests, police said.

A total of 20 people are now in police custody in connection with last week”s failed bombings, police said.

Peter Clarke, the head of London”s police anti-terrorist unit, has called Omar”s arrest &#34an important development in the investigation.&#34 But he warned on Wednesday that the three remaining bombers still presented a danger.

Security was tight at many subway stations in central London on Thursday, three weeks on from the July 7 attacks on three subway trains and a bus that killed 56 people, including the four suicide bombers, and a week on from the failed July 21 attacks.

Residents in Tooting said police had arrested three Turkish men from a fast food takeaway selling halal burgers. Halal is meat from a herbivore slaughtered in a humane way, as Islam requires.

Raja Kumar, who runs a 24-hour convenience store next to the restaurant, said dozens of officers raided the property at 4:30 a.m.

&#34Police said to us stay inside and then they took away three people from the shop, a man aged about 45 called Ali who has been living there for two years and two younger men aged about 28 and 26,&#34 he said.

Six other men were arrested from a property in nearby Garratt Terrace, a street opposite the Tooting Broadway subway station.

Omar, a Somali citizen with British residency, was arrested in a dramatic raid by dozens of anti-terrorist police and bomb disposal experts, some in heavy body armor.

Interrogations of Omar may be key to determining whether last week”s failed attacks are linked to the July 7 suicide bombings. Omar is suspected of trying to blow up the Warren Street subway station last Thursday.

Kati Stewart, 31, a health care worker who lives across the street from Omar in the Small Heath neighborhood of Birmingham, said she”d seen four men coming and going frequently over the past two weeks. &#34They would come at 2a.m., and then when you looked in the morning, the car had gone,&#34 she said.

But Omar, a refugee from Somalia who came to Britain in 1992, generally attracted little attention in the diverse neighborhood, where residents of many ethnic backgrounds and faiths, Indian, Pakistani and Irish; Christian, Hindu and Muslim, say they live together peacefully.

ABC News, meanwhile, reported that British authorities investigating the July 7 attack had found 12 bombs and four improvised detonators in the trunk of the car of one of the suspected suicide bombers 56 kilometers (35 miles) outside of London five days after the deadly explosions.

The network broadcast photos of the findings, including a glass bottle apparently packed with explosives and covered in nails that could be used as shrapnel, and said they provided important clues about who was behind the attacks.

Other raids were carried out on Wednesday in south London”s Stockwell district, where officers arrested three women on suspicion of &#34harboring offenders,&#34 and on two more London homes, where no arrests were made but forensic tests were conducted, police said.

A second July 21 suspect has been named as Muktar Said Ibrahim, 27, also known as Muktar Mohammed Said. He came to Britain in 1990 from Eritrea, his family said. He was granted residency in 1992 and British citizenship in September 2004, the Home Office said. Said was part of a gang that carried out a series of muggings in the mid-1990s but qualified for early release in 1998, the British news agency Press Association reported. When he left prison, Said had a beard, had adopted Islamic dress and was very devout, Press Association said.

Police are also looking into whether Said attended the Finsbury Park or Brixton mosques in London, once considered magnets for radical Islamic clerics, and whether he met shoe-bomber Richard Reid, who is serving a life sentence in a U.S. prison after a failed attempt in 2001 to blow up an airplane, the news agency said.

Meanwhile, in the Netherlands, Dutch prosecutors said on Wednesday that the man jailed for life for murdering filmmaker Theo van Gogh will be charged as a leader of an Islamic terror network believed to have plotted attacks against politicians.

The plans to charge Mohammed Bouyeri for his role in what prosecutors call the Hofstad Network were revealed at a custody hearing for 11 other alleged members.

Bouyeri, 27, was convicted and sentenced to life imprisonment on Tuesday for Van Gogh”s murder, which judges ruled was an act of terrorism. Other alleged members of the Hofstad group were rounded up in the weeks following Van Gogh”s Nov. 2 slaying.

Prosecutors say they were plotting to kill conservative members of parliament Geert Wilders and Ayaan Hirsi Ali, both prominent critics of Islamic extremists.

The Hofstad Network members share an interpretation of Islam, known as Takfir, which calls for the death of non-Muslims, said prosecutor Alexander van Dam.

&#34Nonbelievers represent a threat to ”true Muslims” and must be fought until death. This death threat applies to the entire Western society,&#34 he said.

Van Dam described Bouyeri as a leader of the group who distributed texts inciting other members to use violence to further the aim of replacing democracy with Islamic theocracy.

&#34The suspects are not only his friends, but his students, followers and confidants,&#34 he said in court. &#34Mohammed Bouyeri is one of the most important suspects in the investigation. The group was formed and focused around him and was largely inspired by his writings&#34.

On Friday, the same court will arraign Rachid Belkacem, 32, who was ordered extradited to the Netherlands by British authorities.

Belkacem, who was arrested in east London in June on suspicion of belonging to the Hofstad group, dropped his fight against extradition last week. With Bouyeri, he would be the 14th alleged member of the group to be charged.

Another teenager who was detained as part of the network was released last May for lack of evidence but still faces charges.

The trial is expected to begin in December after a final custody hearing in September.

Prosecutors have had little success in winning convictions after arrests intended to pre-empt an attack. The latest setback came last April when Samir Azzouz, 18, was acquitted of charges of a terrorist conspiracy to bomb the parliament, Amsterdam”s Schiphol Airport or a nuclear reactor.

Although the session on Wednesday was the third preliminary hearing for the group, the security surrounding the Rotterdam District Court was elevated to unprecedented levels, with a high solid metal barrier blocking access the courthouse.

The Netherlands reinstated border controls after the recent London terror attacks and several prominent officials considered potential targets are under increased protection.

The alleged spiritual leader of the Hofstad group, Syrian national Redouan al-Issar, reportedly has been arrested in Damascus, and another alleged group member identified as Chechen national Bislan I. is fighting extradition in France.