* Details emerge of group of young men who carried outattack
* Most from privileged background, adding to sense of shock
* Bangladesh garment industry braced for investment fallout
* Al Qaeda's South Asian wing urges Muslims to attack inIndia (Adds quotes from police, expert)
By Aditya Kalra and Serajul Quadir
DHAKA, July 4 (Reuters) - Bangladesh police sought moreinformation on Monday from friends and family of the mensuspected of carrying out a deadly attack on a restaurant in thecapital, and some are believed to have attended top schools andcolleges at home and abroad.
The gunmen stormed the restaurant in Dhaka's diplomatic zonelate on Friday and killed 20 people, most of them foreignersfrom Italy, Japan, India and the United States, in an assaultclaimed by Islamic State.
It was one of the deadliest militant attacks to date inBangladesh, where Islamic State and al Qaeda have claimed aseries of killings of liberals and religious minorities in thelast year while the government says they were carried out bylocal groups.
Whoever was responsible, Friday's attack marked a majorescalation in the scale and brutality of militant violence aimedat forcing strict Islamic rule in Bangladesh, whose 160 millionpeople are mostly Muslim.
Islamic State posted pictures of five fighters it said wereinvolved in the atrocity to avenge attacks on Muslims across theworld.
"Let the people of the crusader countries know that there isno safety for them as long as their aircraft are killingMuslims," it said in a statement.
Posts on Facebook identified the men, pictured on an IslamicState website grinning in front of a black flag, as NibrasIslam, Rohan Imtiaz, Meer Saameh Mubasheer, Andaleeb Ahmed andRaiyan Minhaj.
Most went to prestigious schools or universities in Dhakaand Malaysia, officials said. One of them was the son of apolitician.
A police officer said the pictures of four of the attackersmatched the bodies, although he gave a different name for thefourth.
Rohan's father, a mid-ranking leader of Prime MinisterSheikh Hasina's ruling party, had lodged a complaint in Januarythat he had gone missing since Dec. 30, 2015, a police officersaid.
On Monday, there was nobody at the family apartment in anaffluent neighbourhood of Dhaka, and a security guard said theparents had left the house on Sunday.
"A majority of the boys who attacked the restaurant camefrom very good educational institutions. Some went tosophisticated schools. Their families are relatively well-to-dopeople," Bangladeshi Information Minister Hasanul Haq Inu toldIndia's NDTV.
TRACING ROOTS
Several posts on social media said the man identified bypolice as Nibras Islam attended Monash University in Malaysia. Afriend who knew him while he studied at Dhaka's North SouthUniversity told Reuters that Islam later went to Monash.
Two others went to an elite public school in Dhaka calledScholastica.
Saifaul Islam, another investigator, said police wereholding two people suspected of involvement in the assault, including one detained soon after the attack.
"We have two persons with us, but we don't know if they arevictims or suspects. They are currently undergoing treatment andwe'd get to know about their role in the incident only afterthey recover."
Nobody had yet come forward to claim the bodies of the sixdead men, he said. "We are taking DNA samples of them and willsee if it matches with the families. We have some suspicions, weknow some boys had gone missing over the last two-three months."
Just days after the attack claimed by its rival jihadimovement Islamic State, a regional branch of al Qaeda urgedMuslims in India to revolt and carry out lone wolf attacks.
The call by al Qaeda in the Indian Subcontinent (AQIS)follows warnings by security officials and experts that the twogroups are trying to outdo each other in the region and claimthe mantle of global jihad.
Rohan Gunaratna, a professor of security studies atSingapore's Rajaratnam School of International Studies, said theDhaka gunmen's background may have helped them mount the attackat the Holey Artisan restaurant, popular with the city'swell-heeled and foreigners.
"As they were well educated and young, they could blend intoand operate in the upmarket diplomatic enclave without evokingred flags," he said.
"The IS (Islamic State) attack team was also technologicallysavvy and they uploaded the photos during the attack both to(the) IS command cell in Bangladesh and IS central in Syria."
On Monday, hundreds of people gathered in central Dhaka toremember the victims, holding placards in different languages.
"We bleed from similar veins, we cry. Bangladesh, stand upfor the next fight," read one large banner written in English.
The attack could be a huge blow for Bangladesh's $26 billiongarment industry, as fears mount that major retailers from Marksand Spencer to Gap Inc could rethink their investments.
Japan's Fast Retailing Co, owner of the Uniqlo casual-wearbrand, said it will suspend all but critical travel toBangladesh and has told staff there to stay home.
(Additional reporting by Zeba Siddiqui in MUMBAI, Rupam Jainand Tommy Wilkes in NEW DELHI and Ruma Paul and ReutersTelevision in DHAKA; Writing by Sanjeev Miglani and TommyWilkes; Editing by Mike Collett-White and Nick Macfie)
Marks & Spencer (MKS)