KABUL – Taliban militants fired at least nine rockets at the Afghan capital before dawn on Tuesday in the biggest attack of its kind for several years, some landing near major Western embassies, police and witnesses said.

Amid an escalation of violence before August 20 presidential elections, two rockets struck the Wazir Akbar Khan diplomatic area, home to both the U.S. and British embassies as well as the headquarters of the NATO-led International Security Assistance Force (ISAF).

The Taliban have vowed to disrupt the elections and have called on Afghans to boycott the ballot, the second direct presidential poll since the Islamists were toppled by U.S.-backed Afghan forces in 2001.

Violence across Afghanistan this year had already reached its worst level since 2001 and escalated further after thousands of U.S. Marines launched a major offensive in the Taliban stronghold of Helmand in the south last month.

At least one rocket landed near a hospital close to the U.S. embassy, television pictures showed.

Other rockets landed in different areas of the city, shattering windows and startling residents in the pre-dawn darkness. One child was wounded.

Separately, a provincial governor escaped unhurt after roadside bombs hit his convoy just west of the capital in an apparent assassination attempt, a spokesman said.

Residents said Tuesday's rocket attack was the biggest for several years. It was also the first serious attack in Kabul in this year's upswing of violence, which has gradually spread out of Taliban strongholds in the south and east.

The Taliban claimed to have fired 12 rockets at Kabul, with the city's combined military and civilian airport their target.

An ISAF spokeswoman said the force had heard reports that between five and 12 rockets were fired at Kabul. None landed in the ISAF base but investigations were under way, she said.

GOVERNOR ESCAPES BOMBING

Speaking at a campaign rally in Gardez in Afghanistan's east, President Hamid Karzai again urged Taliban militants to take part in the elections rather than target the poll.

I invite them to come for voting and for peace in this country, Karzai told supporters in Gardez.

The Taliban have repeatedly rejected such overtures, saying no peace talks would be possible until all foreign troops have left Afghanistan.

Mohammad Halim Fedaye, governor of Maidan Wardak province just west of Kabul, was unhurt after his convoy was hit by roadside bombs on Kabul's western outskirts on Tuesday, a spokesman for Fedaye said. There were no other casualties.

The attack on Fedaye was the latest in a string of ambushes and bombings aimed at candidates, campaign officials and election offices in the past two weeks. A vice-presidential running mate of Karzai's was among those attacked but was also unhurt.

Also on Tuesday, a suicide bomber killed four civilians and an intelligence official in southern Zabul province, police said.

On Monday, a roadside bomb attack claimed by the Taliban killed at least 12 people in the normally peaceful western city of Herat, an important commercial hub near the Iranian border.

At least nine foreign troops, including six Americans, were killed at the weekend, mainly in the south and east.

The U.S. military has poured thousands of extra troops into Afghanistan in recent months, with NATO members sending smaller numbers, in a bid to help secure the election.

The extra troops are part of U.S. President Barack Obama's wider new regional strategy to defeat the Taliban and its Islamist allies and stabilize Afghanistan.

With Washington identifying Afghanistan as its major military priority, the election is seen as a test of Obama's new strategy and of Kabul's ability to stage a credible and legitimate ballot.

(Additional reporting by Ismail Sameem in KANDAHAR and Samar Zwak in GARDEZ; Editing by Paul Tait and Sanjeev Miglani)