Pakistan's key opposition party led by former Prime Minister Imran Khan has accused police of detaining hundreds of its supporters in raids.
A policeman was killed during one of the raids that started early on Tuesday, when a person opened fire on policemen who had entered his house in the city of Lahore.
Fawad Chaudhry, a spokesperson for the party, said police launched the operation shortly after midnight on Monday.
Homes of the party's supporters were still being raided on Tuesday morning and at least 400 supporters from the party were arrested across the country, Chaudhry said.
Khan condemned the arrests on Twitter. Authorities confirmed the raids but refused to share details about any arrests.
READ MORE:Pakistan's Imran Khan calls for march on Islamabad to press early polls
Police crackdown
Interior Minister Rana Sanaullah accused Khan of seeking to create a civil war-like situation. The minister confirmed a policeman was killed in one of the raids.
"More than 200 supporters of PTI (Pakistan Tehreek-e-Insaf) have been arrested in Punjab," a police official in Lahore, the capital of Pakistan's largest province, told AFP news agency on condition of anonymity.
"We have raided their houses and have arrested many of them."
A second official, asking not to be named, provided the same information, adding that those arrested had been booked on public order offences and remain in detention.
In Islamabad, large shipping containers were placed on a key road leading to the parliament building, to prevent Khan's supporters from getting close and possibly staging a sit-in there.
Earlier this week, Khan had urged his supporters to gather in the capital on Wednesday for a demonstration that he said would continue until the government announced a date for snap elections.
Khan, who served as prime minister for over three and half years, was ousted by a no-confidence vote in parliament in April. He was replaced as prime minister by Shahbaz Sharif.
Khan claims his removal was the result of a US-organised plot. Washington denies any role in Pakistan's internal politics.
READ MORE:Pakistan boosts Imran Khan's security after his claim of deadly plot
