Pakistan became a new focus for the wide-ranging investigation into the attacks on London as the country’s authorities said two of the four suspected suicide bombers visited Karachi last year.

Photographs issued by Pakistan’s immigration authorities showed two suspects, Shehzad Tanweer, 22, and Mohammad Sidique Khan, 30, arriving in Karachi in November aboard a Turkish Airlines flight. They, returned to London in February. Pakistani officials also said Hasib Hussain, 18, thought responsible for the Tavistock Square bus bombing, arrived in Karachi last July aboard a Saudi airliner. But it was not clear from his passport details that he had been identified correctly.