By Asad Hashim and Jibran Ahmad

ISLAMABAD/PESHAWAR, Pakistan (Reuters) - Pakistan's prime minister said on Friday his government is using "formal and informal channels" to seek the return of seven passengers of a crashed helicopter Pakistani helicopter who were captured by the Taliban in Afghanistan.

A Taliban commander claimed the seven were "in safe hands" with the insurgents.

The Pakistani government helicopter, en route to Russia for a routine overhaul, crash-landed in the Taliban-held Logar province in eastern Afghanistan on Thursday.

"Formal and informal channels are being used to ensure safe recovery of the entire crew," Prime Minister Nawaz Sharif said in a statement from his office.

Pakistan's army chief, General Raheel Sharif, called Afghan President Ashraf Ghani on Friday to request his country's help.

"Afghan President Ashraf Ghani assured all possible assistance in this regard," tweeted General Asim Bajwa, the Pakistani military's spokesman on Friday.

Logar province has been increasingly lawless since the launch two years ago of a military operation in neighboring Pakistani tribal areas pushed many Taliban and allied fighters into Afghanistan.

On Friday, a senior Afghan Taliban commander, speaking on condition of anonymity, confirmed that the passengers - six Pakistanis and a Russian technician - were in their custody and that negotiations for their release were ongoing.

"They are being looked after, being provided tea, food, everything," he said. "We are in touch with the Pakistani officials. We conveyed to them that they are in safe hands."

He added that it was no use seeking help from the Afghan government or U.S. military, because the Taliban are in full control of the district.

The Pakistani government and military did not directly confirm direct talks with the Taliban, but officials said they were doing everything possible.

"Efforts are in top gear for early recovery of the crew & pilots of the chopper... Prayers for my dear friends safe return," tweeted Shahbaz Sharif, the prime minister's brother and chief minister of the Punjab provincial government that operates the helicopter.

The aircraft had permission to fly over Afghan air space on its way to Uzbekistan further north, said Nafees Zakaria, the Pakistani Foreign Ministry spokesman, on Thursday.

Pakistan's army chief had previously contacted top U.S. commander in Afghanistan General John Nicholson asking for his international military coalition's help in recovering the men, Bajwa said on Thursday.

(Additional reporting by Andrea Shalal; Writing by Asad Hashim; Editing by Kim Coghill)