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Taliban insurgents launched a brazen, four-hour ground attack against the biggest NATO base in southern Afghanistan, following up a barrage of rockets and mortars fired at the Kandahar Airfield base, officials said Saturday.

Rockets began hitting Kandahar Airfield shortly after dark, at about 8 p.m. local time, said U.S. Navy Commander Amanda Peperseim, a spokesperson for NATO forces at the base.

She said a ground attack was launched soon after at least five rockets and mortar rounds fell on the base.

Peperseim said a number of NATO personnel were wounded, but had no information on the nationalities, number or condition of the wounded. The Canadian Press reported Saturday evening that there were no confirmed fatalities in the attack.

Another official with the NATO force said the casualties included both civilian and military personnel.

As people on the base scurried for cover in bunkers, the boom of artillery and the rattle of gunfire could be heard in the distance. A loudspeaker announcement said the ground attack was coming from the north side of the base.

Maj. Robert Kelly told The Canadian Press that the attack struck closer than anyone could have expected.

"It was loud enough to make you really duck down and say, 'Whoa, that was pretty close."'

Troops had to don flak jackets and grab their weapons during the attack. At least five rockets and mortars were fired, but no insurgents entered the base after troops mounted a counteroffensive.

Maura Axelrod, a reporter with HDNet who was inside the base, said she could hear heavy outgoing fire and that commanders had come into the bunker where she had taken cover to order all U.S. Marines with weapons to help in establishing a security perimeter.

Freelance journalist Tom Popyk told Â鶹ӰÊÓ Channel that the attack was quickly beaten off.

"The coalition spokesperson tells me that was totally unsuccessful. It was just a few insurgents, basically small-arms fire," Popyk said in a telephone interview. "This attack on KAF was not well co-ordinated; it was small and was based on the north side of the sprawling air base perimeter."

"This can only really be described as basically a suicide attack by the Taliban. There was no way they were going to get inside the perimeter and certainly there was no way they were going to survive this attack."

Kandahar Air Field -- known as KAF for short -- is home to an estimated 30,000 soldiers and civilian workers, including more than 2,500 Canadian troops making up a battle group. It's also a headquarters for the southern Afghan region.

It is not unusual for the Taliban to launch sporadic rocket attacks on the sprawling base, built around an airstrip half an hour's drive south of Kandahar City.

Most of these attacks have come in the form of badly aimed Chinese rockets, propped up against a pile of rocks, crudely aimed at the NATO base and fired remotely. They usually do little damage, even when they hit the base.

But the Taliban has largely avoided engaging in head-to-head combat with coalition forces since 2006, when a series of operations by Canadian soldiers culminating in Operation Medusa killed hundreds of Taliban fighters in Kandahar province.

This is believed to be the first ground assault on the heavily fortified Kandahar Airfield since the Taliban was swept from power in 2001.

Alan Bell, an international security analyst based in Toronto, told Â鶹ӰÊÓ Channel that the attack was audacious, but essentially unsuccessful.

"Attacks by rockets are not rare. They usually fire a few rockets from outside the perimeter fence, into Kandahar Airfield … what is new is that they've actually had the audacity to attack it on the ground," he said.

"KAF has such a large perimeter there are places you can penetrate without oversight. But there's so many soldiers, so many people there protecting that base that it'll be a short-lived battle."

The base is the staging area for thousands of additional U.S. forces, which have been pouring into the country over the past few months in preparation for a summer offensive against the Taliban.

This is the third major assault on a NATO base in Afghanistan in the past six days.

On Tuesday, a Taliban suicide bomber attacked a NATO convoy in Kabul, killing 18 people including six NATO soldiers.

Canadian Col. Geoff Parker, the highest ranking Canadian casualty in Afghanistan to date, was among the dead.

On Wednesday, dozens of Taliban gunmen attacked the enormous U.S. military base at Bagram Air Field, killing an American contractor in fighting that lasted more than eight hours.

The attacks came soon after the Taliban announced a spring offensive against NATO forces and Afghan government troops -- their response to a promise by the Barack Obama administration to squeeze the Taliban out of their strongholds in southern Kandahar province.

Bell said the Taliban is likely mounting such attacks just to show that it can.

"These type of attacks are their way of showing the Afghanistan government and the (coalition) forces that they still have the ability to mount these attacks … it's going to get worse as we go through the summer as opposed to better."

Prime Minister Stephen Harper said the attack shows the danger of the conflict.

"Obviously it reminds us that our men and women in uniform in all capacities over there, including on the airfield, do face constant danger," Harper said, speaking in Dryden, Ont.