Boston bombs 'remote trigger'

US Vice President Joe Biden today spoke at the memorial for Sean Collier, a police officer killed in the search for the Boston marathon suspects.

Biden commended all who attended the memorial, saying that people's determination "resonated around the world".

The Vice President Joe Biden and his wife Jill are among attendees at a memorial service to honour Officer Sean Collier, who was shot and killed on 18th April in the aftermath of the Boston Marathon bombings. Authorities expected around 10,000 people to attend.

Read more: Funeral for woman killed in Boston bomb blasts begins

US officials are holding talks with relatives of the Tsarnaev brothers, who are suspected of carrying out the Boston bombings, in Dagestan, according to media reports.

BBC News reports that a delegation from the US Embassy in Moscow flew in to the Russian republic last night. News agency AFP reports that the FBI was involved in the interviews.

The eldest of the two brothers, Tamerlan, spent six months in Dagestan and his native Chechnya last year.

Watch our correspondent Martin Geissler's interview with their mother here

Boston Mayor Tom Menino has revealed $20 million (£13.1 million) has been raised in global donations towards victims of the city's marathon bombing.

The wife of deceased Boston bomb suspect Tamerlan Tsarnaev and her family are "trying to come to terms" with the shock that he and his brother allegedly masterminded the attacks.

A statement read out by Miriam Weizenbaum, the lawyer for Katherine Tsarnaeva, said:

Read: Mum of Boston bomb suspects reveals they attended marathon last year

The condition of Boston Marathon bombing suspect Dzohkhar Tsarnaev has been upgraded from "serious" to "fair", the US Attorney's Office has said, according to Reuters.

Read: Boston Marathon suspect could face death penalty

The number of people hurt in the Boston Marathon bombing has risen to 264, with officials confirming the city's hospitals faced a significant second wave from spectators and runners hurt in the April 15 blasts.

Many people waited a few days before seeking medical attention for complaints such as ringing in ears and minor shrapnel wounds, the Boston Public Health Commission said.

The increase added to the initial figure of 180 people said to have been injured in the aftermath of the twin explosions.

Three people were killed and at least 14 people lost all or part of a limb.