KABUL (Reuters) - Taliban suicide fighters launched an attack on central Kabul on Tuesday, taking over a multi-storey building under construction near the diplomatic district in the Afghan capital and firing rockets in the direction of several embassy and NATO compounds.

The assault was the second major Taliban attack in the city in under a month after suicide bombers targeted the British Council headquarters in mid-August, killing nine.

Loud explosions were interspersed with gunfire through the early afternoon, and at least two rockets landed in the upmarket Wazir Akbar Khandistrict, home to the U.S., British and many other embassies.

One hit a school bus, but it appeared to have been empty at the time of impact. Four wounded civilians had been taken to hospitals, a deputy health minister said.

Two NATO helicopters circled the building in central Abdul Haq square, which the attackers had taken over. The Taliban said the group was armed with rocket propelled grenades, suicide vests and AK-47s.

"The primary targets of the attackers are the intelligence agency building and a ministry," Taliban spokesman Zabihullah Mujahid told Reuters by phone from an undisclosed location. He later said they were also attacking the U.S. embassy and the headquarters of the NATO-led International Security Assistance Force (ISAF).

Shafiullah, an agent from the National Directorate of Security who was working near the scene of the attack, said the attackers were firing rockets toward the U.S. embassy and other targets.

A U.S. embassy spokesmen said all staff had taken shelter.

"Right now the embassy is in duck and cover," U.S. embassy spokesman Gavin Sundwall said. "We're still assessing the situation." Sundwall said he was not able to confirm witness reports that a sniper was firing into the embassy.

Police and other security officials blocked roads around the U.S. embassy and other diplomatic missions, and said there were five attackers.

"There are five attackers involved but I can not give you more details because the operation is ongoing," said Mohammad Zahir, head of Kabul's Criminal Investigation Unit.

Violence in Afghanistan is at its worst since U.S.-backed Afghan forces toppled the Taliban government in late 2001, with high levels of foreign troop deaths and record civilian casualties.

Taliban attackers laid siege to a British cultural center in the Afghan capital in mid-August, killing at least nine people during an hours-long assault on the 92nd anniversary of Afghanistan's independence from British rule.

In late June, insurgents launched an assault on a hotel in the capital frequented by Westerners, killing at least 10.

(Writing by Emma Graham-Harrison; Editing by Nick Macfie)