(Adds new attack in west)
By Rafiq Shirzad
JALALABAD, Afghanistan, Aug 30 (Reuters) - Taliban suicide bombs hit an office of the Afghan intelligence agency in an eastern city on Saturday, killing six people, and insurgents shot dead another 11 in the west, in an upsurge of violence as foreign combat troops prepare to withdraw from the country.
Seven militants were also killed during several hours of heavy fighting with Afghan security forces at the Jalalabad headquarters of the National Directorate of Security (NDS), said Ahmad Zeya Abdulzai, a spokesman for the governor of eastern Nangarhar province near the border with Pakistan.
Abdulzai said four NDS agents and two civilians were killed when a truck and a smaller car, both loaded with explosives, were driven into the compound and a gunfight broke out between Afghan forces and the insurgents.
Reuters was not able to reach the NDS immediately for comment. The Taliban claimed responsibility for the attack, in which dozens were wounded.
A pattern of bold offensives by militants has emerged across Afghanistan in recent weeks during the summer "fighting season."
It coincides with political deadlock in the capital, Kabul, where rival presidential candidates have failed to resolve months-long disputes over an election meant to mark the first democratic transfer of power in Afghan history.
Most foreign combat troops are due to leave by the end of 2014 but the election dispute has meant a prolonged delay in signing a security pact with the United States governing how many troops would remain.
On Saturday, the insurgents struck in the western province of Farah, stopping a truck carrying workers to a construction site near the Iranian border and killing 11 of them. Authorities were trying to find out why the workers were targeted.
"They were innocent Afghan workers. They did not have any connection to the government, so we don't know the reason for the attack," said Jawad Afghan, a spokesman for the provincial governor.
As the political impasse drags on, the Taliban-led insurgency has focused on important tactical and symbolic targets as a challenge to the Afghan security forces who are taking over from their NATO-led counterparts.
Afghan forces have struggled to fight off large numbers of insurgent fighters in provinces to the east, north and south of Kabul.
"This is part of an alarming trend across the country," said Graeme Smith, a senior analyst at the International Crisis Group in Kabul. Taliban offensives "are longer in duration, bigger in size and against more ambitious targets than we've seen previously."
In northern Kunduz province, security forces were in a stand-off with insurgents in a weeks-long battle for control over the province that was the last Taliban stronghold before they were driven out by the U.S.-backed Northern Alliance in 2001.
"The insurgents are better armed than us," said Kunduz police chief Mustafa Mohseni. "They use heavy machine guns, RPGs (rocket-propelled grenades) and 82mm rockets against our forces."
A Kunduz police spokesman said security forces were concentrated on a district just next to the provincial capital. Many Kunduz residents have fled to nearby provinces to escape the violence and some who remained show little enthusiasm for the government's effort to hold back the insurgents.
"There is no job, no security, no life," said Kunduz shopkeeper Sayed Malek. "We don't care if the Taliban come back and take over the whole country. We want a peaceful life." (Additional reporting by Mirwais Harooni and Hamid Shalizi in Kabul; writing by Krista Mahr and Sanjeev Miglani; editing by Tom Pfeiffer)