Minsk, Sep 8 (IANS): Belarusian opposition leader Maria Kolesnikova has reportedly been detained at the country's border with Ukraine a day after she was reported missing, a state-media report on Tuesday.

According to the report, Kolesnikova, one of three women who joined forces to challenge President Alexander Lukashenko in the August 9 election, was held at the border early Tuesday morning, the BBC reported.

It comes a day after witnesses reportedly saw masked men bundle her into a minibus.

But reports of the opposition figure's whereabouts were conflicted as officials have not confirmed what has happened to her, and it remains unclear as to what exactly happened at the border crossing.

The Belarusian Co-ordination Council - a body set up by the opposition to oversee a transfer of power after the disputed election - said it had no idea of her whereabouts, adding that press secretary Anton Rodnenkov and executive secretary Ivan Kravtsov had also disappeared.

But Ukraine has confirmed that only the two men had arrived.

Kolesnikova was initially the campaign manager for presidential candidate Viktor Barbaryko before his arrest in June, when she decided to work with Veronika Tsepkalo and Lukashenko's main rival Svetlana Tikhanovskaya, reports the BBC.

Tikhanovskaya is now in Lithuania after she was forced to leave Belarus following the election which the incumbent President won by 80 per cent of the votes, while she garnered only 10 per cent of the ballots.

Tsepkalo has travelled to Poland with her husband and children.

Another female activist, Olga Kovalkova, announced on September 5 that she had fled to Poland amid threats of imprisonment.

Belarus has witnessed mass unrest since the election results were announced, which has also claimed the lives of at least four people and injured hundreds others.

Authorities said more than 600 people were arrested on Sunday on the fourth consecutive weekend of anti-government demonstrations.