A suicide bomber driving a truck packed with explosives killed at least 41 people at a busy market in southeastern Afghanistan on Tuesday, the deadliest attack in the war-torn country for months.
The huge blast in Urgun district of Paktika province came hours after a remotely controlled bomb targeted a presidential palace media staff bus in Kabul, killing two and wounding five.
The explosion at Urgun also destroyed dozens of cars and shops, Hamkimullah, a witness, told AFP.
"There is no room in the hospitals for the victims. People are treating the wounded people on the streets," he said.
UN Secretary-General Ban Ki-moon condemned the bombing "in the strongest possible terms".
"The attack on civilians in Paktika during the holy month of Ramadan is a despicable criminal act, which killed and injured many innocent people, including children," his spokesman said.
The blasts highlight the fragile security situation Afghanistan faces as NATO progressively withdraws its 50,000 remaining combat troops, leaving local forces to battle a resilient Taliban insurgency.
Afghanistan is also in a delicate state politically, with the two rivals to succeed President Hamid Karzai only narrowly avoiding a crisis at the weekend over allegations of electoral fraud.
Karzai's office said in a statement that 41 people including six children and the imam of a mosque were killed and 67 wounded in Paktika.
This makes it the deadliest attack in Afghanistan since a suicide bombing at a mosque in northern Faryab province in October 2012 that killed 42 people.
The deadliest before that was a suicide blast at a shrine in Kabul on the Shiite holy day of Ashura in December 2011 that killed 80.
There are fears that the death toll from Tuesday's attack could rise -- the spokesman for Paktika's governor, Mokhlis Afghan, said 43 had died.
Interior ministry spokesman Sediq Sediqqi said the explosives were placed in a truck and detonated after police tried to stop the vehicle in the market.
Paktika borders Pakistan's tribal areas including North Waziristan, where the Pakistani military are in the midst of a major offensive against militants.
Hundreds of fighters are thought to have fled across the border into Afghanistan.
- Soaring civilian deaths -
There was no immediate claim of responsibility and the Taliban denied they were behind the blast in a tweet from a recognised account. They regularly deny attacks that kill civilians.
The head of the UN mission in Afghanistan, Jan Kubis, condemned the attack and called for those responsible to be brought to justice.
As part of their annual spring offensive, the Taliban have increased attacks on foreign and Afghan security forces, but it is usually civilians who suffer the brunt of the casualties.
A UN report last week said civilian casualties in Afghanistan soared by 24 percent to 4,853 in the first half of 2014 compared to the same period in 2013.
Ground combat is now causing more deaths and injuries than improvised explosive devices in a worrying sign of spreading conflict, the UN report said, with women and children increasingly caught in the crossfire.
The grim figures underline the fragile security situation Afghanistan faces as it wrestles with political turmoil over its disputed presidential election, with most foreign forces due to withdraw by the end of the year.
The two candidates vying to take over from Karzai, Abdullah Abdullah and Ashraf Ghani, reached a deal late Saturday to audit all eight million ballots cast in their runoff election following two days of frantic diplomacy by US Secretary of State John Kerry.
Afghanistan had teetered on the brink of disaster last week after preliminary results of the disputed runoff were released showing Ghani well ahead of his rival.
Abdullah, who had already complained of fraud in the vote, declared himself the true winner and said massive cheating had robbed him of victory.
The bitter impasse raised fears of a return to the ethnic violence of the 1990s. Ghani is supported by the Pashtun tribes of the south and east while Abdullah draws his support from Tajiks and other northern Afghan groups.
Both candidates have agreed to stand by the results of the audit, with the winner to be declared the next president.