Islamabad, Pakistan (CNN) Former Pakistani Prime Minister Nawaz Sharif and his daughter have been arrested and are being held in Islamabad after they flew back from the United Kingdom to face prison sentences, authorities said.

The return to Pakistan of Sharif and his daughter, Maryam, on Friday comes one week after a court found them guilty of corruption-related charges and sentenced them to 10 and seven years in prison, respectively.

They first flew from London to Lahore, where authorities took them into custody and escorted them onto a small government plane, which took off for Islamabad, a source who was on the first plane told CNN on condition of anonymity.

In a video released early Friday morning by the Pakistan Muslim League Nawaz (PML-N) party, Sharif could be seen addressing his supporters from inside an airplane, stating that he was returning to Pakistan as a "sacrifice for the future generations of the country and for its political stability."

"The country is at a critical juncture right now. I have done what I could," he said. "I am aware that I have been sentenced to 10 years and will be taken to a jail cell straightaway."

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