Afghan President Hamid Karzai has cancelled a planned visit to Britain to return home after yesterday's sectarian attacks, which killed 59 people.
The largest of the bombs targeted a Shia Muslim shrine in the capital Kabul.
The events wipe out any residual optimism from an international conference about the future of Afghanistan, held on Monday in Germany, and refocused attention on the fragile Afghan security situation.
The NATO-led International Security Assistance Force (ISAF), responsible for security across much of the country, says it is winning the war against the Taliban.
But if yesterday's bombing sets a precedent for violence between the Sunni Muslim majority and the Shia minority, it would severely stretch army and police resources.
At a funeral ceremony today for victims of the attack, hundreds of Shia Muslims carried the bodies of the dead.
They chanted that because they had been killed at a Muslim ceremony, they had died in the name of the Prophet Mohammad.
Some said immediately after the Kabul blast that police had not done enough to protect them.
Hundreds of worshippers had gathered to mark the festival of Ashura at a shrine in central Kabul when a suicide bomber struck.
Among those killed was a US citizen, the American embassy in Kabul said in a statement. It gave no further details.
At the German conference, the Afghan government's Western backers - who have spent billions of dollars on the country since the US-led overthrow of the Taliban government in 2001 - pledged to support the country beyond the end-2014 deadline for the withdrawal of foreign combat troops.
Afghanistan has said that it will not be able to afford the army and police force it needs after 2014 without international help.
