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By Caroline Davies in Islamabad & Robert Greenall in London
BBC News
Supporters of Pakistan's main opposition leader Imran Khan have clashed with police outside his home as officers try to arrest him.
Police fired tear gas shells to disperse the supporters, who threw stones and bricks.
There is a tense situation outside the compound, in the city of Lahore, as police try to force their way in.
He is facing allegations he unlawfully sold state gifts while in office. He says the case is politically motivated.
Police have made previous attempts to arrest him, but Mr Khan, 70, told the BBC he thought they were determined to put him behind bars this time.
"I'm mentally prepared that I'm going to be spending my night in a cell," he said. "I don't know how many nights, but I'm all prepared for that."
The former prime minister appeared in front of what he said were cannisters of tear gas, which he said had been fired into the compound of his home.
He said 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."
His supporters are also holding protests in other cities.
Mr Khan was ousted as prime minister last April but has kept up pressure on his successor Shehbaz Sharif with demonstrations and regular speeches, calling for elections due by the later this year to be held early.
He blames Mr Sharif for an assassination attempt at a rally in November which saw him wounded in the leg.