The hijackers forced the plane to land at Larnaca airport, in Cyprus, where police said the gang threatened to blow up the plane if it was not refuelled and flown on to London.
The authorities said they believed the hijackers were seeking political asylum in the UK. Airports in Britain were alerted to the incident and were standing by last night.
The Sudan Airways Airbus 310 was en route from Khartoum to Amman, Jordan, when it was hijacked 20 minutes after take off.
Police in Cyprus confirmed that the plane landed at Larnaca at around 11:15 pm local time (8.15pm UK time).
It emerged later that the gang originally wanted to fly to Rome but changed their minds and forced the pilot to set a course for Cyrpus.
Glafcos Xenos, a police spokesman, said the hijackers told air traffic controllers that they were armed with grenades and TNT, and that one had said: "We will blow up the plane" if their demands were not met.
It was not clear how many hijackers were on board, but air traffic controllers said that the pilot had referred to the hijackers in the plural. The nationality of the hijackers was also unclear.
Mr Xenos added that the gang refused a request from the Cypriot authorities to allow women and children to leave the plane while it was on the ground at Larnaca airport, but promised authorities that they would free all the plane's passengers and crew once the plane was on the ground in London.
The director of the civil aviation authority in Cyprus, Michael Herodotou, said the plane was initially refused permission to land at Larnaca but that it was granted when air traffic controllers learned it was running out of fuel.
Communciation channels between the hijackers and authorities on the ground were being kept open by messages being relayed through the pilot of the aircraft.
Security was tight at Larnaca airport last night, with hundreds of police officers drafted into the the surrounding area. Hospitals and emergency services were put on red alert.
This is the second hijacking this year involving a Sudanese airliner. On March 24, a Sudan Airways Airbus A320 plane carrying 40 passengers and crew on an internal flight was hijacked and forced to land in Eritrea.
The two Sudanese hijackers who seized that plane sought political asylum in Eritrea. They surrendered to Eritrean authorities immediately after reaching Asmara, the Eritrean capital.
The Muslim fundamentalist government in Sudan has been fighting a 13- year civil war with rebels who want autonomy. The rebels are mostly Christians in the country's southern region and adherents of tribal faiths. More than 1.3 million people have died in the conflict and the famines it has brought.
Sudan gained independence from Britain 40 years ago this year. Since then, the country has been mostly ruled by military dictatorships, with elected governments ruling for just 10 years.
Just before midnight, Cypriot authorities granted the hijackers' request to refuel the plane. Ground crews at Larnaca began to refuel the airliner as it sat on the tarmac, surrounded by police.
It was still unclear if the airliner would be allowed to take off and make the four-hour flight to London, or whether permission would be granted by air traffic controllers in this country.
Police confirmed that none of the 186 hostages or 13 crew members on board had been released by the armed gang.
The hijacking comes at the peak of Cyprus' holiday season as hundreds of Europeans are taking their summer break on the island.Reuse content