By Adrian Croft
LASHKAR GAH, Afghanistan (Reuters) - A bomb exploded near a police station outside a crucial city in Afghanistan's south Tuesday where Afghan forces are readying to assume security responsibility within hours, another worrying sign as insurgents seek to disrupt a gradual transition process.
The roadside bomb hit a police vehicle near a newly built police station in Bolan, just outside the bustling market city of Lashkar Gah.
Lashkar Gah is due to be handed to Afghan forces on Wednesday. It is the most contentious of seven areas on the list for handover this week in the first phase of a transition process that will end with all foreign combat troops leaving Afghanistan by the end of 2014.
Initial reports suggested there were no casualties in the blast, said Kamaluddin Khan, a senior provincial policeman.
But it was a worrying sign less than 24 hours before the formal handover from British to Afghan troops. Violence has spiked across Afghanistan in the lead-up to the transition process.
Mehtar Lam, another relatively peaceful district in Laghman province, east of Kabul, was handed over from U.S. forces on Tuesday in a flag-raising ceremony attended by Ashraf Ghani, the head of Afghanistan's transition process.
"The Afghan national army has had an enormous change both in quality and in numbers. For the seven locations which have been selected for tranche one, we are completely confident that the Afghan army will have the capability," Ghani said.
Of the seven areas -- two provinces, three cities and two districts -- to be handed over to Afghan control this week, most are in areas considered relatively safe.
Lashkar Gah, however, is the "most difficult" of the seven, Ghani said, and one that will be seen as a critical test of the readiness of Afghan forces to assume control.
Ghani said despite the difficulties, Afghan forces had already taken control of the city.
"Come with me tomorrow and you will see that in Lashkar Gah there are no international forces," he said.
British commanders in Lashkar Gah have said this week's handover was a formality and would change little on a day-to-day basis because Afghan forces have been gradually assuming control over the past year.
But there will still be a British troop presence in Lashkar Gah long after Wednesday's ceremony. The British have a large base inside the city and still conduct operations with Afghan forces in outlying districts.
The volatility in Lashkar Gah and surrounding areas hit home after Tuesday's blast and the killing of seven policemen near the city the previous day.
Monday, seven policemen manning a checkpoint in a small town outside Lashkar Gah were poisoned and then shot dead by a police colleague, the spokesman for Helmand's governor said. The policeman who had also been manning the post then escaped with their weapons and a police vehicle, Daoud Ahmadi said.
A spokesman for the NATO-led International Security Assistance Force (ISAF) in Helmand said its troops were called in to assist after the incident at the request of Afghan police.
The Taliban initially claimed responsibility but the killings now appear to be the latest in a series of incidents where "rogue" Afghan soldiers and policemen have turned their weapons on their Afghan colleagues or foreign mentors.
President Hamid Karzai's spokesman, Waheed Omer, said on Monday insurgent infiltration in the army and police had become a "reality." He also warned efforts to disrupt the transition process and "disable the government" had increased.
In Nad Ali, a district neighboring Lashkar Gah, two civilians were kidnapped and then killed, the Helmand governor's office said in a statement.
Violence across Afghanistan in 2010 hit its worst levels since the Taliban were overthrown by U.S.-led Afghan forces in 2001, with civilian and military casualties hitting record levels, and this year has followed a similar trend.
The first of the seven areas to be formally handed over on Sunday was Bamiyan, one of the safest of Afghanistan's 34 provinces and long an anti-Taliban redoubt.
The handover ceremony in Bamiyan, attended by senior Afghan ministers, was conducted in relative secrecy and with minimal media coverage, a reminder of how tense the country remains as violence increases and spreads to once-peaceful areas.
Facing criticism over Sunday's event, the Afghan government scrambled to make amends, with an ISAF helicopter shuttling journalists to Tuesday's ceremony in Mehtar Lam.
(Additional reporting by Samar Zwak in Mehtar Lam, Ismail Sameem in Kandahar and Abdul Malek in Helmand; Writing by Jonathon Burch; Editing by Paul Tait)