ISLAMABAD, Pakistan — A former prime minister of Pakistan was arrested on Thursday, as the government escalated what it describes as an anticorruption campaign and opposition parties have denounced as a political vendetta.

The former leader, Shahid Khaqan Abbasi, who remains a senior figure in the opposition Pakistan Muslim League-Nawaz, was arrested at a highway toll plaza while on his way to a party news conference in the city of Lahore, and presented with a warrant accusing him of involvement in “corruption and corrupt practices.” The authorities did not immediately offer more details.

The current prime minister, Imran Khan, who won last year’s general elections on a strong anticorruption platform, has repeatedly vowed that he will arrest politicians involved in corrupt practices. Opposition figures have accused him of using the anticorruption campaign to distract from his handling of Pakistan’s economic difficulties, troubles for which he blames previous governments.

Mr. Abbasi is a loyalist of the ousted prime minister Nawaz Sharif. He was named prime minister in August 2017 after Mr. Sharif was disqualified by the Supreme Court following a corruption inquiry, and held that office until May 2018.