Two American soldiers have been seriously injured in a grenade attack in the Afghan capital, Kabul, the US military says.

An Afghan interpreter who was with them was also wounded in the blast, less than a kilometre from the presidential palace.

This is the first time that American soldiers have been injured in an attack in the Afghan capital.

It comes at a time when President Hamid Karzai is in the Norwegian capital, Oslo, to urge donors to continue their support for his country's economic and security programmes.

Nearly 8,000 American troops are in Afghanistan involved in the hunt for al-Qaeda fighters or ousted Taleban members.

Explosions

The head of Kabul's police force, Basir Salangi, says his officers have arrested two men in connection with the attack.

It came just as it was getting dark in one of the capital's busiest districts.

President Karzai is seeking help from donors

American soldiers are a regular sight on Kabul streets. They are heavily armed, wear body armour and travel in convoys.

There have been several explosions near the US embassy in recent months.

The authorities have blamed them on remnants of Osama Bin Laden's al-Qaeda network and the deposed Taleban.

Security concerns

Kabul has seen a number of blasts over the past year.

The most serious was a car bomb that went off in early September, and left 26 people dead and dozens more injured.

Afghan police said they had averted a potentially deadly explosion at Kabul's main mosque during the Muslim Eid-al-Fitr festival recently.

The BBC's Kylie Morris in Kabul says the latest attack will raise concerns in a city which has enjoyed relatively good security, compared with the rest of the country.

The capital is patrolled by nearly 4,700 troops from more than 20 countries who make up the International Security Assistance Force (Isaf).