Zeina Khodr, reporting for Al Jazeera from Afghanistan, said: "Western dignitaries and foreign diplomats ... all stay at this luxury hotel and really it's a symbol of foreign presence.
"A [Taliban] spokesman told Al Jazeera that four attackers were involved in this operation, one suicide bomber and three other attackers."
She said the spokesman had said the hotel was targeted because "that is where the leadership of the enemy stays".
Some reports of the attack differed, with one police officer saying: "There was gunfire inside and outside the hotel, plus a suicide attack, we don't know anything about casualties, it is very complicated at this time."
Another police official said that two attackers had thrown hand grenades, killing two guards, then moved past the security cordon and into the hotel compound where they both exploded suicide vests.
Khodr said interior ministry officials had not confirmed the nationalities of the six people killed in the attack.
Norwegian officials said a Norwegian foreign ministry employee and a Norwegian journalist were among those injured and had been taken to hospital.
Norwegian television stations said the injured journalist worked for the Dagbladet daily newspaper.
Jonas Gahr Stoere, Norway's foreign minister, was at the hotel at the time of the attack and afterwards hid in the basement, NRK, Norway's public broadcaster, reported.
Stoere was later taken to a secure location, the foreign ministry in Oslo said in a statement.
Afghan police and US troops surrounded the scene after the attack.
Norway has about 500 soldiers in Afghanistan as part of a Nato-led international force sent there after US and Afghan opposition forces ousted the Taliban government in 2001.