London Tube bombing: 18-year-old man arrested by Kent Police in Dover

London: An 18-year-old man has been arrested by Kent Police in Dover in connection with London Tube bombing.

"We have made a significant arrest in our investigation this morning," Neil Basu, Senior National Co-ordinator for Counter Terrorism Policing, said in a statement.

Britain deployed hundreds of soldiers at strategic sites on Saturday to free up police to hunt those behind a bomb which injured 29 people on a packed commuter train in London and triggered the country`s highest security level.

Islamic State (IS) has claimed responsibility for the explosion on a packed London Underground train which was about to depart Parsons Green underground station at 8.20 am (0720 GMT) on Friday.

"The bombing on a metro in London was carried out by a detachment of the Islamic State" group, it said in a statement published by its Amaq propaganda agency.

UK Prime Minister Theresa May announced the national threat level would be raised to "critical", meaning another attack may be imminent.

The explosion -- Britain`s fifth terror attack in six months -- sparked a "wall of fire" that left passengers with burns and caused a stampede of panicking people in which some were trampled.

Nobody suffered life-threatening injuries in the incident, the fifth terrorist attack Britain has suffered in less than six months. They are being treated in hospitals mainly for burn injuries.