Khan was detained at his home in Islamabad as he prepared to take out a march from Rawalpindi to Islamabad, which he had announced a couple of days back, according to leaders of his party, the Tehrik e Insaf.

Imran Khan's house arrest came as the Islamic alliance Muttahida Majlis-e-Amal and opposition parties observed a 'Black Day' today to protest against the American leader's visit.

Khan wanted to take out the rally to protest against Bush's backing to President Pervez Musharraf [Images], which he charged had 'seriously undermined' the political parties' efforts to restore democracy in the country.

Khan was also detained in Lahore [Images] last week for attempting a similar rally.

Besides Khan, 26 of his associates were taken into preventive custody by teh authorities ahead of the rally, party leaders said.

Prior to his visit to Pakistan, Bush referred to Musharraf as his 'buddy' and praised the General's 'vision of democracy' in an interview. 'I believe that he is committed to having a reform process come to fruition and I believe he is committed to free and open elections,' Bush had said.

Khan, who earlier used to be a supporter of Musharraf, has aligned closely with the the MMA in carrying out anti-Musharraf and anti-US demonstrations.

'The reason why I am protesting against Bush's policies is his endorsement of Musharraf's so-called vision for democracy which is making us a fool. If generals make such good leaders, he should propose a military general for presidency in America,' Khan had said earlier.

Khan also condemned the government's efforts to prevent political parties from holding protest demonstrations against Bush's visit, while tens of thousands of people organised protest rallies in India during the US President's just concluded visit there.

Khan claimed that Musharraf was once again strengthening his image as a military dictator in the world. He said he did not know how blocking peaceful protests would serve Musharraf's agenda of promoting a soft image for Pakistan.

Besides Khan, Pakistan's beleaguered opposition parties agitating against Musharraf's military rule have decided to boycott the US President's visit.

While moderate opposition parties like the Pakistan Peoples Party declined to join the MMA protests, they agreed to boycott the dinner being hosted by Musharraf tonight for Bush.

The opposition boycott would be headed by Leader of the opposition and MMA general secretary, Maulana Fazlur Rehman.