Taliban fighters have freed 14 inmates from a jail in western Afghanistan after staging a daring prison break, police have said.

Mohammad Faqir Askar, a provincial police chief, said the fighters blew up the main gates of the prison in Farah city after planting a bomb on Sunday.

"Twenty prisoners escaped but we arrested six of them soon after the incident and 14 are still at large," Askar said.

He said four other inmates had been injured in the blast at the facility where at least 400 prisoners are currently being jailed.

Askar blamed the blast on Taliban fighters who have been waging a bloody insurgency since they were ousted from power during the US-led invasion nearly nine years ago.

In November 2009, 13 prisoners escaped from the same prison via a tunnel and in June earlier that year, at least to 1,000 Taliban inmates escaped from Sarpoza prison in Kandahar city after a suicide attack blew open the front gates and destroyed the walls.

Kabul blast

Also on Sunday, a suicide bomber detonated explosives in central Kabul, killing at least four people and injuring at least 30, according to the Afghan Health Ministry.

"He was trying to get to a specific area but because of high security the bomber was forced to detonate on a street where there is little activity," said Zemarai Bashary, spokesman for the interior ministry.

The attack comes just two days before Kabul is due to host a major international donors conference, set to be attended by up to 40 foreign ministers, including US secretary of state Hillary Clinton.

"Security is on track," Bashary said on Saturday.

"We're determined to provide good security for the Kabul Conference."

He said "thousands" of police officers, soldiers and intelligence agents had been deployed "in vulnerable areas" of the Afghan capital as well as remote villages to thwart any Taliban attack plans.

Earlier, Nato announced that international and Afghan forces had foiled a plot to attack the conference.

Several "enemies of the people" were killed and 26 people were arrested in the Friday-night raid in the Kabul neighborhood of Wasel Abad, according to Nato and the Afghan defence ministry.

PHOTO CAPTION

US soldiers patrol the perimeter fence of the high-security Pul-e-Charkhi Prison in Kabul.

Al-Jazeera