* Truck bomb, car bomb before gunfight-provincial official
* Taliban claims attack, violence increased in past week
Seven people were killed in an attack claimed by the Taliban on a base operated by Polish and Afghan forces in eastern Afghanistan on Wednesday, officials and a Reuters witness said.
Ghanzi province's deputy governor said the attackers detonated an explosive-laden truck at the rear of the base and a car bomb at the main gate, before a six hour gunbattle inside involving up to 10 of the 15 assailants.
Four policemen and three civilians were killed, and 10 Polish soldiers and 52 Afghan security force members and civilians had been wounded by the time the fighting ended around 10 p.m., Ahmadullah Ahmadi said.
Violence has intensified across Afghanistan this week as Taliban insurgents seek to increase pressure on NATO contingents preparing to withdraw by the end of 2014.
Another 20 people died in a spate of bombings elsewhere in the country over the past 24 hours.
Claiming responsibility for the attack on the base, the Taliban said a suicide bomber detonated himself near a truck loaded with explosives.
"The bombing wiped out the security posts and the first checkpoint while other fighters, armed with heavy and light weapons, managed to get inside," Taliban spokesman Zabihullah Mujahid said in an email.
Gunshots rang into the night following the attack at around 4 p.m. A Reuters witness saw column of black smoke rising from the base in the provincial capital.
Elsewhere in Afghanistan, two attacks in Helmand province on Wednesday killed three soldiers, 10 Afghan civilians and wounded more than 20 other people, police and provincial officials said.
One of the attacks took place in Helmand's provincial capital Lashkar Gah, where a suicide bomber blew himself up near a foreign troop convoy but without killing or wounding any of the soldiers targeted, a spokeswoman for the NATO-led force said.
In the second attack, on the outpost of Nad Ali in Helmand, a suicide bomber in a car killed three soldiers, officials said.
Helmand has been the scene of some of the fiercest fighting between NATO-led forces and the insurgents since the overthrow of the radical Islamist Taliban in 2001.
On Tuesday, in the western province of Farah, Taliban insurgents torched 40 trucks that supply NATO-led forces with fuel and killed six Afghan drivers, the provincial governor's spokesman, Abdul Rahman Zhwanday, said.
And in Kabul, a suicide bomber targeted a government ministry, killing himself and one other person, according to security sources in the capital.