Last week Sotirios Mousouris, the UN Secretary-General's Special Representative to Afghanistan, visited Kabul and met Mr Najibullah for the first time in seven months. The UN and all embassies, except those of Pakistan and Iran, withdrew their staff from the city in November because of the civil war between President Burhanuddin Rabbani and the Prime Minister, Gulbuddin Hekmatyar. Neither of the warring factions is in a position to guarantee the security of UN staff. Although Mr Hekmatyar has been appointed Prime Minister, he has not entered the city and is still based at his military camp 20 miles (32km) to the south.
Diplomatic sources said that Mr Najibullah had appealed to the UN to free him so that he can fly out and seek medical treatment for a worsening kidney infection. His wife and children are in India. With him in the UN compound are his brother, a bodyguard, his former chief of staff, General Torkhi, and the general's wife and three children. They are being looked after by local Afghan UN staff. The children are reported to be extremely depressed. Pakistan, India and several other countries have offered Mr Najibullah asylum.
Sources said that Mr Najibullah's spirits are still high, that he reads voraciously, exercises occasionally and watches BBC World Service Television on satellite. He has helped build a bunker in the compound to escape the rain of rockets launched by Mr Hekmatyar that have destroyed much of the city. On Friday, 100 rockets fell on Kabul, killing 15 people and wounding dozens more.
In separate meetings with Mr Mousouris, both President Rabbani and Mr Hekmatyar pleaded with the UN to return its staff to Kabul. But the UN maintains that it cannot do so because of a lack of security and also insists that Mr Najibullah must first be freed. The UN is both embarrassed and fed up about acting as a prison warder for the former president.
President Rabbani is not strong enough to order Mr Najibullah's release on his own because it would open him to criticism from other factions. In a meeting in December, both Afghan factions demanded that Mr Najibullah be tried for treason.
However, with Afghanistan isolated from the outside world, suffering severe food and medicine shortages and with international relief agencies refusing to work in Kabul, all the factions now realise the need for the UN to return. The UN knows this and is playing a skilful diplomatic game to persuade the mujahedin to agree to Mr Najibullah's freedom.