Riot police fired live bullets in the air and clashed with dozens of opposition supporters in Ethiopia's capital Tuesday, a day after arresting and revoking the licenses of 30 taxi drivers who took part in renewed protests against the disputed May 15 elections.

There was no immediate word on casualties from clashes between the federal police and protesters in Merketo, the main business center in Addis Ababa. Protests against alleged electoral fraud in June saw police kill at least 42 people.

"There has been gunfire and rioters are clashing with the police. There are riot police who have been stoned, but as yet we have no reports of any casualty," said Adam Melaku, head of the independent Ethiopia Human Rights Council.

The riots began on the day the government threatened legal action against the main opposition Coalition for Unity and Democracy, or CUD.

The party has been boycotting Ethiopia's lower house of parliament, saying it wants a solution to the contested results of the May parliamentary election before taking up its seats.

The party has 109 seats in the 547-member Council of People's Representatives. Opposition parties have claimed that hundreds of their supporters and members have been arrested in the past two months.

"Taking the CUD to court for its stance against the constitution is timely," the government said in a statement.