Insurgents were repelled after launching an attack on NATO's main military base in southern Afghanistan, home to the largest contingent of Canadian Forces personnel in the country, an official said Saturday.

Militants attempted to breach the perimeter of Kandahar Airfield but did not break through, said Squadron Leader Paul Scott, a spokesman for the International Security Assistance Force.

Rockets and mortars were used in the attack and personnel on the base were injured, Scott said. But he did not say how many injured, or the types of injuries. The nationalities of those hurt were not immediately known.

Details have also not been released on the estimated number of insurgents involved in the attack or how many of them might have been killed or injured.

Everyone on the base was instructed to remain in safe locations as a precaution until the attack ended at about midnight.

Earlier, NATO forces spokeswoman Master Sgt. Sabrina Foster said rockets started hitting Kandahar Airfield around 8 p.m. local time, followed quickly by a ground assault.

Five rockets hit the base as people rushed to take cover in bunkers, CBC's Darrow MacIntyre said.

Those reached by telephone said they could hear the boom of artillery and the rattle of gunfire in the distance.

According to a loudspeaker announcement, the ground attack was coming from the north side of the base.

Prime Minister Stephen Harper and Defence Minister Peter MacKay were both told of the attack and were monitoring developments.

"I have been briefed on the attack, I've been informed about it, but it would probably be a bit premature for me to comment on it at any length," Harper told reporters on Saturday during an appearance at an event in Dryden, Ont. "Obviously it reminds us that our men and women in uniform in all capacities over there, including on the airfield, do face constant danger."

Kandahar Airfield, just outside Kandahar City, is the launching pad for thousands of additional U.S. forces pouring into the country for a summer surge against the Taliban.

Escalation part of Taliban offensive

Last Wednesday, insurgents staged a brazen overnight assault on another key coalition base north of Kabul.

They fired rockets, small arms and grenades into the U.S.-run Bagram Airfield after suicide bombers blew themselves up at the front gate.

Ten insurgents were killed and seven U.S. soldiers were wounded during more than eight hours of fighting. An American contractor was also killed.

On Tuesday, a Taliban suicide bomber attacked a NATO convoy in the capital, Kabul, killing 18 people including six NATO service members. One was Col. Geoff Parker, 42, the highest-ranking Canadian officer killed in the Afghan conflict.

The attacks are part of a Taliban spring offensive targeting NATO forces and Afghan government troops.

With files from The Associated Press and The Canadian Press