A news conference setting out the latest developments following the London bombings is taking place.

Commissioner of the Metropolitan Police Sir Ian Blair and Assistant Commissioner Specialist Operations Andy Hayman are appearing at the conference.

Here is the latest:

Ian Blair: More than 50 fatalities.

Still bodies on tube train between Russell Square and King's Cross.

Twenty-two people in a critical condition in hospital. Three hundred and fifty people treated in hospital, 100 detained. One person died in hospital. Seven hundred casualties in all.

Said police had "implacable resolve" to track down terrorists. Said police "will bend every sinew" to find bombers.

Definitely only four sites of blasts. Absolutely nothing to suggest it was a suicide bombing attack although nothing can be ruled out.

Andy Hayman: Forensic investigation suggests each bomb had less than 10 pounds of high explosive.

Each device on tube trains was likely to be on the floor of the carriage. Bus bomb may have been on floor or on seat.

Investigation will depend on forensic evidence from "very challenging" scenes.

Police have not yet got near carriage where bomb was on Russell Square/King's Cross train.

Public need patience as investigation cannot be rushed.

Police need the help of the community to gather information.

Asked people to ring Terrorist Hotline on 0800 789 321.

Ian Blair: Has all the hallmarks of al Qaeda but nothing specific to prove this yet.

"Blindingly obvious" there might still be an al Qaeda cell in operation in UK.

Overwhelmed by offers of help from Europe and USA.

Don't know whether claim on al Qaeda website is real.

Andy Hayman: Bombs would have been in rucksack-sized bags or carriers.

Ian Blair: Nothing to suggest any intelligence has been missed.