Media playback is unsupported on your device Media caption Video footage from Zaranj shows injured civilians including children

Forty-eight people have been killed and more than 130 others wounded in a series of bombings in the south-west and north of Afghanistan.

Many of the victims were shopping for the weekend's Eid celebrations at the end of the Muslim month of Ramadan.

Thirty-six people were killed in four suicide bombings in Zaranj near the Iranian border in the south west.

Shortly afterwards, police in the northern province of Kunduz said 12 people were killed in another blast.

More than 30 others were reported wounded.

The district governor of Dasht-e Archi district in Kunduz told the BBC the bomb had been placed on a motorbike and had gone off in a main square shortly before the end of the day's Ramadan fast.

Many of the victims were thought to be civilians, including children and food vendors.

The BBC's Aleem Maqbool in Kabul says the bombings follow a series of deadly attacks by infiltrators in the Afghan security forces, against their colleagues as well as coalition troops.

The surge in violence comes as international troops gradually hand over responsibilities to Afghan security forces, with Nato preparing to pull out of the country by the end of 2014.

'Blood all over'

In both Kunduz and Nimroz province in the south-west, the bombers were said to have attacked crowded markets.

Afghan President Hamid Karzai, on a visit to Saudi Arabia, condemned the attacks, saying the bombers did not care about Ramadan.

Intelligence officials in Zaranj told the BBC that as many as 14 potential suicide bombers had infiltrated the city. Some had been arrested on Monday, with further arrests early on Tuesday.

One official said he had been searching for further suspected insurgents in a crowded marketplace when the attacks began.

"There have been heavy casualties; the majority of them are civilians," deputy police chief Mujibullah Latifi told AFP, adding that some of the attackers had been killed by police.

Reports say two of the bombers' explosives were detonated when police fired on them.

An eyewitness, Mohammad Zalmay, told the BBC: "I was buying sweets with my sons and daughters when I heard a bang. I fell to the ground. When I woke up, I saw blood all over."

According to unconfirmed reports, 11 of the dead were police officers.

Nato commander Gen John Allen condemned the bombings as "intentional mass murder". In a statement, he called on Taliban leader Mullah Omar to "rein in his murderers".

Nimroz is considered a relatively peaceful province but last Saturday an Afghan policeman opened fire on his colleagues in Dilaram district, killing 11 people.

Last week, seven soldiers with the Nato-led force in Afghanistan were killed in incidents involving Afghan forces.

US Defence Secretary Leon Panetta told reporters in Washington he was very concerned about the "so-called green-on-blue or insider attacks [in Afghanistan]... because of the lives lost and because of the potential damage to our partnership efforts".