At least four people were killed when a suicide car bomber attacked a convoy of foreign soldiers in the Afghan capital, Kabul, Saturday, officials said, with an unspecified number of NATO-led troops among other casualties.

Three civilians and a police officer were killed in (the) Kabul attack today, an interior ministry spokesman said on his Twitter account, without giving further details.

The attack on the International Security Assistance Force (ISAF) convoy took place in the Darulaman area in the west of the city, near the national museum.

The former royal palace, now in ruins, is also in the area, along with several government departments.

Several ISAF members are recorded as casualties and there are also several local Afghan casualties, a spokesman for the NATO-led force said, without specifying whether the victims had been killed or wounded.

Violence across Afghanistan is at its worst since the start of the war 10 years ago, according to the United Nations, despite the presence of more than 130,000 foreign troops.

ISAF says there has recently been a fall in attacks by insurgents but this data excludes attacks that kill only civilians and attacks on Afghan security forces operating without international troops.

Thursday, insurgents armed with rifles and rocket-propelled grenades attacked two bases used by foreign troops in southern Afghanistan. An Afghan interpreter working for ISAF was killed in that attack, which stretched into Friday before the last of the four insurgents were killed.

There has been a series of high-profile assassinations, as well as day-to-day attacks by Taliban raiders, over the past year.

In the most spectacular recent attack, insurgents launched a 20-hour assault on the U.S. embassy and ISAF headquarters in Kabul in September. More than a dozen people were killed in that assault.

(Reporting by Hamid Shalizi and Christine Kearney; Writing and additional reporting by Daniel Magnowski; Editing by Paul Tait)