By Aaron Maasho

ADDIS ABABA, June 17 (Reuters) - An Ethiopian opposition party said on Wednesday that one of its candidates, who took part in last month's elections, was beaten to death in a "brazen attack" it believes was politically motivated.

A government spokesman denied that Prime Minister Hailemariam Desalegn's government was involved in any way.

The Horn of Africa country has won plaudits for delivering growth for much of the past decade, but rights groups often accuse the government, which has won every seat announced so far in the May election, of clamping down on dissent.

Samuel Awoke, a Semayawi Party candidate in the north-central Amhara Region at the May 24 vote, was attacked on Monday evening in Debre Markos, less than 300 km (190 miles) north of the capital Addis Ababa, party chairman Yilekal Getinet said.

"His attackers approached him at 7:30 in the evening and beat him to death, right in the middle of the street on his way home," Yilekal told Reuters.

"It was a brazen attack carried out on an individual who was critical of the government and who was a victim of a previous assault on election day. This was not some petty crime - it must have been politically motivated," he said.

A second government official confirmed the incident but rejected claims of political foulplay, saying Samuel - a lawyer - was attacked by a client aggrieved over his handling in court of a dispute over land.

"The attacker is in custody while another individual is being investigated," the government spokesman, Shimeles Kemal, told Reuters. "There was nothing political about it."

The ruling Ethiopian People's Revolutionary Democratic Front coalition swept all 442 seats announced so far, out of a total 547. The opposition held a sole seat during the last term.

Critics and the opposition say the government has quashed dissent, jailed bloggers and journalists for their views and may have rigged elections. The government denies the charges, saying it guarantees free speech and conducts fair elections. (Editing by Drazen Jorgic and Louise Ireland