Police in Islamabad have clashed with supporters of former Pakistan Prime Minister Imran Khan as he arrived in the city to appear in court.
Police said Mr Khan's supporters threw stones and fired tear gas near the court complex.
Mr Khan is appearing in court to address charges that he sold state gifts while in office, which he denies.
As he travelled to the capital, police raided his home in Lahore and made arrests.
Earlier in the week Lahore police tried to arrest Mr Khan after he missed a court hearing, and officers clashed with supporters outside his home.
On Friday, the court granted Mr Khan protection against arrest on the assurance that he would appear in court on Saturday.
The ex-PM says the charges against him are politically motivated but says he is attending court "because I believe in the rule of law".
He said attempts to arrest him were unrelated to the court case and instead were "intended to take me away to prison so that I am unable to lead our election campaign".
He told Reuters that he had formed a committee to lead his party, the Pakistan Tehreek-e-Insaf (PTI), in the event of his arrest.
In a sign of the deep divisions within Pakistani politics, the current Prime Minister Shebaz Sharif tweeted that Mr Khan's "antics of the last few days" had "laid bare his fascist and militant tendencies" and accused him of using supporters as "human shields".
About 4,000 security officials, including elite commandos and anti-terrorism squads, have been deployed in Islamabad, AFP reported.
Mr Khan was ousted as prime minister last April in a no-confidence vote but has kept up pressure on his successor Mr Sharif with demonstrations and speeches calling for elections due later this year to be held early.
He blames Mr Sharif for an assassination attempt at a rally in November in which he was wounded in the leg.
He told the BBC this week that the authorities were trying to arrest him to stop his party from taking part in forthcoming elections. But he added: "Whether I am in jail or not they will not be able to stop my party winning."
Police in Lahore said they had arrested Khan supporters who had been involved in violence against police earlier in the week, including for throwing petrol bombs. The operation involved 1,000 security personnel, local media reported.
The Punjab police chief said some officers would remain outside Mr Khan's residence.