"We write today to urge you to use the United States' substantial leverage with Pakistan's government to secure the release of political prisoners including former Prime Minister Khan and curtail widespread human rights abuses," the lawmakers wrote in a letter.

U.S. Representative Greg Casar, who led the letter, said it marked the first such collective call from multiple members of the U.S. Congress for the release of Khan, who otherwise has had testy relations with Washington as a long standing critic of U.S. foreign policy.

Khan has been in jail since August 2023 and has faced dozens of cases since he was removed as prime minister in 2022 after which he launched a protest movement against a coalition of his rivals led by current Prime Minister Shehbaz Sharif. Khan says cases against him, which disqualified him from contesting the February elections, are politically motivated.

He had a fallout with Pakistan's powerful military and blamed his ousting on them. The military denies political interference.

The Democratic lawmakers also raised concerns about reported irregularities in Pakistan's elections.

Pakistan's government denies being unfair in Khan's treatment and its election commission denies the elections were rigged.

Washington says the February vote could not be characterized as free and fair. Britain, the European Union and the United Nations also raised concerns.

Khan did not run, but candidates he backed secured the highest number of seats. Still, his rivals formed a coalition government.

A U.N. human rights working group said in July Khan's detention violated international law.

WASHINGTON, Oct 23 (Reuters)