ISLAMABAD - Former Prime Minister Imran Khan of Pakistan was arrested by paramilitary troops in a major escalation of a political crisis.

The arrest intensified a showdown between the government and Mr. Khan, a populist former cricket star who was staging a comeback after he was ousted from office last year.

His arrest could raise the prospect of mass unrest.

Mr. Khan was at a court hearing in Islamabad when he was arrested by paramilitary troops, a day after the Pakistani military issued a strong statement against the former leader accusing him of making false accusations against a senior intelligence official.

Mr. Khan, who was removed from office in a parliamentary no-confidence vote in April last year, is facing dozens of court cases on charges that include terrorism and corruption.

The arrest instantly intensified a showdown between the government and Mr. Khan, a populist former cricket star, who has staged a political comeback in the months since his removal from office. His party has drawn tens of thousands to political rallies across the country, at which Mr. Khan and others have called for fresh elections and accused Pakistan’s powerful military establishment of orchestrating his ouster.

At the same time, the state has brought dozens of court cases against Mr. Khan. He and his supporters have characterized the accusations as a misuse of the justice system by the government of Prime Minister Shahbaz Sharif and by the military to sideline him from politics. Pakistani political and military leaders have repeatedly denied those claims.

The political tensions surrounding Mr. Khan came to a head in November, when the former prime minister was wounded during a political rally after an unidentified man opened fire on his convoy, in what aides have called an assassination attempt. Since then, Mr. Khan has been mostly ensconced at his residence in Lahore, Pakistan’s second-largest city, and has refused to appear in court in Islamabad, the capital.

Fawad Chaudhry, a top aide to Mr. Khan, said that the threat to Mr. Khan’s life made court appearances much riskier, adding: “It is not humanly possible to make court appearances in such a vast number of cases.”

The drama surrounding Mr. Khan seems only to have buoyed his popularity, analysts say, underscoring his unique ability to outmanoeuver Pakistan’s typical playbook for sidelining political leaders who have fallen out of favour with the country’s powerful military.

Over the summer, his party, Pakistan Tehreek-e-Insaf, or P.T.I., won sweeping victories in local elections in Punjab — a province that has often served as a bellwether for national politics — and in the port city of Karachi.

Those political victories were also seen as a response to worsening economic conditions that the new government has struggled to address, and as a repudiation of the military establishment, which has long wielded a heavy hand in Pakistani politics.