Former Pakistan Prime Minister Nawaz Sharif left his aircraft after a 90-minute standoff with authorities after returning home on Monday from seven years in exile.
A Reuters correspondent aboard his flight saw him leave the plane surrounded by supporters and party officials.
Earlier, Sharif's arrival at Islamabad airport sparked an immediate stand-off with authorities in which he refused to leave the plane unless accompanied by his supporters.
"I feel great, I'm prepared to face any situation," Sharif told a Reuters correspondent aboard his flight, but over an hour after he touched down he remained rooted to his seat.
His return was always going to spark a confrontation with President Pervez Musharraf, the army general who cast him into exile.
Before his arrival, authorities had detained about 4,000 Sharif supporters and several leaders of his Pakistan Muslim League (Nawaz), including the chairman, as well as three leaders of an allied religious alliance, party officials said.
An immigration officer came aboard Sharif's flight after it landed and asked him to come with him, but the 57-year-old declined unless he was accompanied by his supporters and staff -- including his British lawyers.
"I don't think there are any legal obligations that we are not complying with. We want to work with you. Help us, take us to the lounge," said Lord Nazir Ahmed, a member of the British House of Lords travelling with Sharif craft.
Sharif, ousted by Musharraf in a 1999 coup and sent into exile in Saudi Arabia the following year, has returned home despite a Saudi official's plea for him to stay away for the sake of stability.
Musharraf exiled Sharif under what the government says was an agreement that he stay in exile for 10 years. In return, he avoided a life sentence on hijacking and corruption charges.
His return now is a serious challenge for Musharraf, who has lost much support since trying to dismiss the country's top judge in March.
The government says Sharif is breaking his word at a time when Pakistan needs stability in the run-up to elections.
Musharraf is preparing to seek another term in a presidential election in the national and provincial assemblies some time between Sept. 15 and Oct. 15.
A general election is due around the end of the year.
"My ambition is very clear, I have to take Pakistan back to the rule of democracy, because unless we have this, we will continue to be in a state of mess as we are today," he told reporters on his departure from Britain.
Officials of Sharif's PML (N) party said about 4,000 activists, most from Punjab province, Sharif's political power base, had been detained. A provincial police official said 250 "troublemakers" had been picked up.
The Supreme Court said last month Sharif and his brother Shahbaz had the right to return and the government should not try to stop them. Shahbaz is not on the flight from London.
"There's no plan to disrupt their arrival, the question is what happens after ... the law of the land will take its course," Deputy Information Minister Tariq Azim Khan said late on Sunday.
Ordinary people were not able to get closer than three or four kilometres from Islamabad airport. Police with riot equipment were posted at barricades but there was no sign of Sharif supporters. Rallies have been banned.
Travellers with tickets had to get to the airport by shuttle bus, while some workers trying to get home from a night shift were stranded on the wrong side of road blocks.
"Every Pakistani has the right to come here," said Munir Ahmed, a cook, as he watched police at a barricade.
"If he wants to come he should come quietly and not make a political show of it because he had that agreement," said a young man who gave his name as Usman.
Pakistan says the Saudi royal family and assassinated Lebanese leader Rafik al-Hariri had guaranteed the exile deal. Sharif said on Saturday he understood the deal had been to stay away for five years.