BISHKEK (Reuters) - Kyrgyz police used stun grenades on Saturday to disperse hundreds of people attending a protest rally against the detention of a former parliamentary deputy and detained dozens of demonstrators.

The confrontation underscored growing political tensions in the former Soviet republic as it prepares for a presidential election in November. Its two previous presidents were toppled by violent riots.

Authorities detained Sadyr Zhaparov, who Kyrgyz media say plans to run for the presidency, when he returned to the country earlier on Saturday after spending three years abroad in self-imposed exile. He faces charges of taking hostage a government official in 2013.

Shortly after his detention, about 500 supporters rallied outside the security service headquarters in central Bishkek, demanding Zhaparov’s release.

A few hours into the rally, some protesters started scuffling with police and hurling bottles at them, a Reuters correspondent said. Police then forcefully dispersed the rally and the Interior Ministry said it had detained 68 people.

Zhaparov had been a senior member of the Kyrgyz government and an adviser to former president Kurmanbek Bakiyev. After Bakiev was ousted in 2010, Zhaparov became a member of parliament.

But in 2013 Zhaparov was sentenced to 1.5 years in prison on charges of attempting to violently seize power after he and several other lawmakers attempted to force their way into the presidential palace during a public protest.

Zhaparov was released the same year, having served most of his prison time in detention awaiting trial. Also in 2013, his supporters staged another protest where some of them briefly held a provincial government official hostage.

Several protesters stood trial for hostage-taking, but Zhaparov was able to leave the country in 2013, only returning on Saturday.

Pro-Russian President Almazbek Atambayev, in power since 2011, cannot run for a second term. Several politicians have announced plans to run, but no clear favorite has yet emerged in the largely Muslim Central Asian nation of six million.

One of the contenders, Omurbek Tekebayev, a former ally of Atambayev who has become one of his fiercest critics, was detained last month and faces trial on charges of corruption and fraud, a move his supporters describe as politically motivated.