KABUL, May 10 (AFP) - The Taliban on Monday declared a three-day ceasefire across Afghanistan to mark this week's Eid al-Fitr holiday, just two days after being blamed for killing more than 50 people - mostly young girls - in a bomb attack outside a school in the capital.

The ceasefire offer comes as the United States continues to pull out its last 2,500 troops from the violence-wracked country despite faltering peace efforts between the Taliban and Afghan government to end a decades-long war.

"Mujahideen of the Islamic Emirate are instructed to halt all offensive operations against the enemy countrywide from the first till the third day of Eid," a statement released by the Taliban said.

"But if the enemy conducts any assault or attack against you during these days, stand ready to robustly protect and defend yourselves and your territory," it added.

Eid al-Fitr marks the end of the Muslim fasting month of Ramadan, and the holiday begins according to the sighting of the new moon. The Taliban declared similar ceasefires last year to mark Islamic holidays.

The government usually reciprocates with a truce. Fraidon Khawzon, spokesman for chief negotiator Abdullah Abdullah, said early Monday: "We welcome the announcement....the Islamic republic is also ready and will announce soon."

The latest offer comes after the government blamed the Taliban for Saturday's attack outside a girls' school in Dasht-e-Barchi, a suburb of the capital largely populated by the Shiite Hazara community, which is often targeted by extremist Sunni Islamist militants.

A series of blasts outside the school - when residents were shopping ahead of the holiday - killed more than 50 people and wounded over 100.

It was the deadliest attack in more than a year.

The Taliban, who denied responsibility, had earlier issued a statement saying the nation needed to "safeguard and look after educational centres and institutions".

The Taliban insist they have not carried out attacks in Kabul since February last year, when they signed a deal with Washington that paved the way for peace talks and withdrawal of the remaining US troops.

But the group has clashed daily with Afghan forces in the rugged countryside even as the US military reduces its presence.