A knee to the groin may be more Vinnie Jones than Machiavelli, but it was no less effective for Evo Morales in asserting his presidential authority.

With one deft movement, Bolivia's combative leader felled an opponent in a football match against a team of political rivals. The receiving player crumpled in agony holding, as local media put it, his "testicular zone".

The incident, during a match on Sunday to inaugurate a renovated stadium in the capital La Paz, was captured on video and last night aired on local TV stations and was uploaded to YouTube.

The friendly match started when, wearing a No 10 green jersey, Morales, a football fanatic and Bolivia's first indigenous president, led his team of bodyguards and officials on to the artificial pitch.

The yellow team was led by Luis Revilla, mayor of La Paz and a political ally turned foe of the president. After smiles and handshakes the game began. Within five minutes Daniel Gustavo Cartagena, in the No 2 jersey for the mayor's team, scythed into the president after he passed the ball, gashing his right leg.

Morales, 50, a former Aymara llama herder and coca farmer, is not known for indulging critics, let alone people who foul him. He walked up to Cartagena, indicated his wound, then kneed him in the groin. The player collapsed, prompting audible whistles from spectators.

The match swiftly deteriorated into a bad-tempered, foul-filled contest which arguably mirrored the Andean country's combative politics. By the end, the match drawn at 4-4, two players from each side had been sent off, including Cartagena and one of the president's bodyguards.

One bodyguard tried to arrest Cartagena after the final whistle, the newspaper La Razón reported, but he was released after Revilla intervened.

Morales denied ordering the arrest but was unrepentant about his response to Cartagena's foul. "I passed the ball and suddenly I received a hammering. It's not the first time it happened," the president told reporters hours later.

Revilla also played down the incident, saying: "This was a football game and on the field we are all players." It was not clear if Cartagena was a member of the mayor's political party, Movement Without Fear.

A medical bulletin from the presidential palace said Morales received a laceration on the inside of the right leg and that a doctor recommended three to four days' rest.

As a young man, Morales's passion on the field for a union of coca-growers' team helped him become union president, launching his political career. Since his 2005 election as the head of the Movement Towards Socialism, which has empowered Bolivia's indigenous people and forged leftist policies, he has become a reserve player for Litoral, an amateur second-division squad.

The leader also hosted a charity match with the former Argentinian player Diego Maradona in La Paz, at 3,597 metres (11,800ft) above sea level, to protest a Fifa ban on games above a certain altitude.