Image caption Terri Chung and Myunghee Bae have campaigned for Kenneth Bae's release

The mother of a US citizen imprisoned in North Korea is being allowed to visit him, his family says.

Terri Chung, the sister of Kenneth Bae, said their mother was in Pyongyang and due to meet him on Friday morning.

Mr Bae, a Korean-American, was arrested last November and sentenced to 15 years' hard labour in May.

North Korea said that Mr Bae - described as both a tour operator and Christian missionary - had used his tourism business to plot sedition.

In a video statement made prior to her departure, Myunghee Bae said she expected to be in North Korea for five days.

"I don't really know what to expect for my trip. All I know is that I want to see my son," she said.

Image caption Kenneth Bae was detained in November 2012 after entering North Korea as a tourist

She said she was grateful to the North Korean authorities for allowing her to visit and expressed shock at the appearance of her son in an interview from prison on 3 July.

"He looked so different and he lost so much weight. I could not believe that prisoner was my son," she said.

Mr Bae's family say his health has deteriorated in recent months and he is suffering from diabetes, an enlarged heart and back pain.

Two months ago, he was transferred from a prison camp to a hospital, they said.

Kenneth Bae (known in North Korea as Pae Jun-ho) was arrested in November 2012 as he entered the north-eastern port city of Rason, a special economic zone near North Korea's border with China.

US detainees in North Korea Eddie Jun Yong-su: Businessman detained for six months in 2011, freed after a visit led by US envoy Robert King

Businessman detained for six months in 2011, freed after a visit led by US envoy Robert King Aijalon Mahli Gomes : Teacher and Christian jailed in 2010 for eight years over illegal entry via China - freed after ex-US President Jimmy Carter visited Pyongyang

: Teacher and Christian jailed in 2010 for eight years over illegal entry via China - freed after ex-US President Jimmy Carter visited Pyongyang Robert Park : US activist crossed into North Korea via China in late 2009 - freed in 2010 by North Korea

: US activist crossed into North Korea via China in late 2009 - freed in 2010 by North Korea Laura Ling/Euna Lee: Jailed in 2009 for 12 years over illegal entry via the Chinese border - freed after ex-US President Bill Clinton met former NK leader Kim Jong-il US citizens held by N Korea

His trial and conviction came at a time of high tension between the US and North Korea, in the wake of the communist state's third nuclear test on 13 February.

It also came as the US and South Korea conducted annual large-scale military exercises, which angered Pyongyang.

Tensions have since eased somewhat. In August, North Korea issued and then revoked an invitation for US envoy Robert King to travel to Pyongyang to seek Mr Bae's release.

North Korea has arrested several US citizens in recent years, including journalists and Christians accused of proselytising.

They were released after visits to Pyongyang by high-profile officials, including former Presidents Bill Clinton and Jimmy Carter.

The US accuses North Korea of using detained citizens as bargaining chips.