Former Pakistani Prime Minister Nawaz Sharif, bottom center, surrounded by aides and supporters on an ariplane as he arrives in Islamabad, Pakistan after he flew from London, England, 10 Sep 2007

Former prime minister of Pakistan Nawaz Sharif has been deported from Pakistan after attempting to enter the country. As Daniel Schearf reports from Islamabad, Mr. Sharif was returning to challenge the military rule of the man who ousted him from power and sent him into exile, Pakistani President Musharraf.

Shortly after his plane touched down at Islamabad airport, black-clad Pakistani commandos escorted Mr. Sharif to an airport lounge. Anti-corruption authorities handed him an arrest warrant. He was deported just a few hours later.

He is back in Saudi Arabia where he has lived in exile for the past seven years.

Mr. Sharif's deportation was not completely unexpected. Officials had warned this might happen if he returned to Pakistan, despite a Supreme Court ruling saying he should be allowed to return without government obstruction.

The government has yet to issue an official explanation.

While being held up in the airport lounge, Mr. Sharif expressed disappointment at not being allowed home.

"Our party leadership is absent. They have not been allowed to come here," he said. "So, we understand that there is an aircraft standing here, there are helicopters. The government has some other plans which we do not know. The telephones are not working, they are all jammed."

Before his arrival, authorities had detained several leaders of Mr. Sharif's Pakistan Muslim League (Nawaz), along with hundreds of supporters. Security was tight at the airport; barbed wire and barricades blocked roads.

The government banned rallies and stopped visitors from entering the airport. But that did not stop hundreds of Sharif supporters from trying. Many of them clashed with police who fired tear gas and used batons against them.

Mr. Sharif had returned to contest upcoming elections against President Musharraf, the general who launched a 1999 coup against him for alleged corruption.

The European Union criticized the decision to send Mr. Sharif into exile again, saying the Supreme Court ruling allowing him back should be respected.

President Musharraf is trying to strike a power-sharing deal with another former prime minister in exile, Benazir Bhutto, who is also expected to try to return to Pakistan.

Mr. Musharraf is supported by the United States as an ally against terrorism. He faces resurgent militants in the border region with Afghanistan, where al-Qaida leader Osama bin Laden is thought to be hiding.

But he has lost significant public support at home. He tried but failed to fire the Supreme Court chief justice in March. The courts are questioning Mr. Musharraf's extension of time as both top general and president.

The deportation, for a second time, of a leading rival, raises the stakes in Pakistan's bitter political struggle.