The arrest of several legislators and leaders of former Pakistani Prime Minister Imran Khan’s party in overnight police raids could trigger yet another showdown between the opposition and the government, analysts have said.

The politicians belonging to the Pakistan Tehreek-e-Insaf (PTI) party were arrested on the premises of Pakistan’s parliament late on Monday, a day after the PTI held a rally on the outskirts of capital Islamabad to demand Khan’s release from prison.

Khan was imprisoned in August last year on several charges. Though his conviction in most cases has either been overturned or suspended, the 71-year-old cricketer-turned-politician continues to remain in jail, facing trial in other cases.

Several rights groups have called for Khan’s release, calling his detention “arbitrary”. A recent indication by the government and the army that Khan could be tried in a military court has further angered the PTI.

Videos on social media showed police officers pushing PTI leaders into vehicles at the National Assembly, the lower house of parliament, after its session concluded on Monday evening. Similar raids were reported from other locations in Islamabad.

While the police said it had arrested four PTI politicians, including its chairman Gohar Ali Khan, the party claims at least 13 leaders were taken into custody.

“Armed, masked men entered the parliament premises and arrested several more party lawmakers,” the PTI’s Sayed Zulfi Bukhari told Al Jazeera. “Many of our lawmakers are currently in hiding, while some are missing after the raid. This is a shocking development and a dark day for democracy.”

The crackdown came a day after PTI’s rally in Islamabad, which was attended by thousands of people who came from all over the country.