Iran's opposition leader Mir Hossein Mousavi vowed Thursday that he would not withdraw for one moment despite of what he described growing difficulties in his web site for the first time.

He said authorities were increasingly isolating and vilifying him in an attempt to get him to withdraw his election challenge.

I am not ready to withdraw from demanding the rights of the Iranian people, he said in a statement posted in his official web site, Kalemeh, adding that he was determined to prove the electoral fraud.

I am ready to show how the electoral wrong-doers….I would not, for the sake of personal expediency and fear in the face of threats, withdraw for one moment my demands for the return of the rights of the Iranian people, whose blood is being unjustly spilled today, the statement said.

In the web site, Kalemeh, Mousavi said he has applied for permission to hold a gathering to commemorate the martyrs of the post-election campaign. The statement did not elaborate or give a date.

In the latest sign of government attempts to silence dissent, the 70 professors were reportedly detained late Wednesday after meeting with Mousavi who led a massive protest rally a week ago.