Survivors of the attacks and relatives of the victims were among those to mark the 10-year anniversary at a ceremony at St Paul's Cathedral in London.
Some stations held silences at 08:50 BST - a decade on from the first bombs.
Earlier, David Cameron was among those who laid wreaths in Hyde Park - where another service will be held later.
The bombings of three Tube trains and a bus - carried out by four bombers linked to al-Qaeda and carrying rucksacks of explosives - was the worst single terrorist atrocity on British soil.
