Five women working on a UN-backed polio vaccination campaign are dead after gunmen, thought to be from the Taliban, attack two Pakistani cities.

Please wait while this video loads. If it doesn't load after a few seconds you may need to have Adobe Flash installed.

Warning - some people may find some of the images within this report distressing

The attacks are thought to be an attempt by the Taliban to counter a UN initiative that the militant group has opposed. They come a day after an unknown gunman killed a male volunteer for the World Health Organisation's anti-polio campaign in Pakistan's largest city, Karachi.

Four of the women killed were gunned down in Karachi, said Sagheer Ahmed, the health minister for surrounding Sindh province. A fifth women was shot in Peshawar in the north west of the country, and later died of her injuries.

The government is in the middle of a three-day vaccination campaign in the highest-risk parts of the country, as part of an effort to vaccinate millions of children under the age of five. Two male workers were also critically wounded in the shootings, said Mr Ahmed, who wrongly reported earlier that one of them had died.

The attack on the polio workers was well-coordinated and occurred simultaneously in three different areas of the city, said police spokesman Imran Shoukat.

Campaign suspended

The government suspended the vaccination campaign in Karachi in the wake of the shootings, according to authorities. The campaign started on Monday and was supposed to run until Wednesday, he said.

Janbaz Afridi, a senior health official in surrounding Khyber Pakhtunkhwa province, said the attacks would not stop the government from continuing its vaccination program in the province and the neighbouring tribal region, the main sanctuary for Taliban militants in the country.

"These incidents are depressing and may cause difficulties in the anti-polio drive, but people should not lose heart," said Mr Afridi. "The government is very serious, and we are determined to eliminate polio despite all odds and difficult conditions."

Taliban opposition

The government, teaming up with UN agencies, is on a nationwide campaign to give oral polio drops to 34 million children under the age of five. But vaccination programs, especially those with international links, have come under suspicion in the country since a Pakistani doctor ran a fake vaccination program last year to help the CIA track down Osama bin Laden.

The Taliban has spoken out against polio vaccination in recent months, claiming the health workers are acting as spies for the US and the vaccine itself causes harm. Militants in parts of Pakistan's tribal region have also said the vaccination campaign cannot go forward until the US stops drone attacks in the country.

The shootings in Karachi on Tuesday all took place in areas mainly populated by ethnic Pashtuns, said Mr Ahmed, the health minister. The Taliban are a Pashtun-dominated movement, and many militants are reported to be hiding in these communities in Karachi.

Polio endemic

The immunisation campaign was previously suspended in Karachi in July after a local volunteer was shot to death and two UN staff were wounded.

Pakistan is one of only three countries where polio is endemic. The virus usually infects children living in unsanitary conditions, attacks the nerves and can kill or paralyse.

Also on Tuesday, two men on a motorcycle hurled hand grenades at the main gate of an army recruiting centre in north west Pakistan on Tuesday, wounding 10 people, police said.

The injured in the attack in the garrison town of Risalpur in Khyber Pakhtunkhwa included civilians and security personnel, senior police official Ghulam Mohammed told the Associated Press. The police have launched a manhunt to trace and arrest the attackers, he said.

No-one immediately claimed responsibility for the attack, the latest in a string of assaults in recent days that illustrate the continued challenge Pakistan faces from militants despite military operations against the Pakistani Taliban and their supporters.