MAZAR-I-SHARIF, Afghanistan (AFP) - At least 10 people died Thursday when Taleban insurgents wearing military uniforms mounted a six-hour gun and grenade siege on a court complex in northern Afghanistan, an assault highlighting the country's fragile security situation.

The attack in the usually tranquil city of Mazar-i-Sharif occurred just before the start of the Taleban's traditional spring offensive, set to be the first fighting season when Afghan security forces battle insurgents without full Nato support.

Explosions rang out as assailants wearing suicide vests lobbed grenades and exchanged gunfire with Afghan security forces, setting ablaze one of the buildings in the compound, according to an AFP reporter at the scene.

Dozens of people were left wounded, with reports of blood shortages in hospitals emerging and urgent appeals for donors circulating on social media.

"Around noon four assailants dressed in military uniforms breached the main gate of the Appeals Court in Mazar-i-Sharif and started firing gunshots and throwing hand grenades inside the complex," said Abdul Raziq Qaderi, the acting provincial police chief of Balkh province.

"Five security personnel and five civilians were killed and 66 others were wounded," he added.

Noor Mohammad Faiz, a senior doctor at the local public hospital, confirmed the toll, adding that some of the wounded were in critical condition.

"Police, prosecutors, court staff, women and children are among those wounded," Faiz told AFP.

The insurgents were holed up inside the complex for six hours, surrounded by a large number of Afghan security forces before they were taken down.

The Taleban claimed responsibility for the attack, which underscores Afghanistan's precarious security situation as US-led foreign troops pull back from the front lines after a 13-year war against the Taleban.

"Our mujahideen have carried out a martyrdom attack... in Mazar-i-Sharif city," Taleban spokesman Zabihullah Mujahid told AFP by telephone.

UPTICK IN ATTACKS

Militant attacks are relatively rare in Mazar-i-Sharif, a city well-known as a melting pot of diverse cultures and religious influences where liberal attitudes coexist with conservative traditions.

Thursday's attack comes a day after an American soldier was killed by an Afghan counterpart in eastern Afghanistan, the first insider attack since Washington announced a delay in troop withdrawals from the country.

Nato's combat mission formally ended in December but a small follow-up foreign force has stayed on to train and support the local security forces.

President Barack Obama last month reversed plans to shrink the US force in Afghanistan this year by nearly half, an overture to the country's new reform-minded leader, President Ashraf Ghani.

Hosting Ghani at the White House for their first presidential head-to-head, Obama agreed to keep the current level of 9,800 US troops until the end of 2015.

The Taleban, who have waged a deadly insurgency since they were ousted from power in late 2001, warned that the announcement would damage any prospects of peace talks as they vowed to continue fighting.

Taleban insurgents have already stepped up suicide attacks on government targets following an Afghan army offensive that began in southern Helmand province more than two months ago.

The uptick in attacks has taken a heavy toll on ordinary Afghans.

The number of civilians killed and wounded in Afghanistan jumped 22 per cent in 2014, a recent UN report said, as Nato troops withdrew from combat.

The United Nations Assistance Mission in Afghanistan attributed the rise to an intensification in ground fighting, resulting in a total of 10,548 civilian casualties last year.

Afghan forces are currently bracing for what is expected to be a bloody summer push by the Taleban and the government has also raised the ominous prospect of the Islamic State making inroads into Afghanistan.