KABUL: Afghan presidential election front-runner Abdullah Abdullah said he had escaped an assassination attempt Friday when an explosion hit his campaign motorcade in Kabul, just days ahead of a hotly-contested run-off election.

“A few minutes ago, when we left a campaign rally our convoy was hit by a mine,” he told another election rally in quotes broadcast on Afghan television.

He added that some of his guards were mildly wounded, while he was unhurt.

The attempt came ahead of the second-round presidential election on June 14, with Taliban insurgents threatening to disrupt the polls.

No one has so far claimed responsibility for the attack.

Abdullah fell short of the 50 per cent threshold needed for an outright victory in the April first round and will face former World Bank economist Ashraf Ghani in the run-off.

“We condemn the attack on respected presidential candidate Dr. Abdullah Abdullah,” Ghani said on Twitter.

“This is the act of the enemies of Afghanistan to disrupt the democratic process in the country. “

President Barack Obama recently outlined the US strategy to end America's longest war, saying that the 32,000-strong US deployment in Afghanistan would be scaled back to around 9,800 by the start of 2015.

Those forces would be halved by the end of 2015 before eventually being reduced to a normal embassy presence with a security assistance component by the end of 2016.

But it relies on Afghanistan signing a long-delayed Bilateral Security Agreement laying out the terms of the US military presence in the country after this year.

The outgoing Karzai refuses to sign the pact, but both Afghan presidential candidates have vowed to sign it if elected.