Kosovo headed for political deadlock on Thursday as lawmakers vying for control following last month's snap elections staged a walkout after failing to agree on a key parliament post.

Parties opposed to Prime Minister Hashim Thaci teamed up in the 120-seat assembly to back his rival Isa Mustafa for the post of parliament speaker.

Mustafa received 65 votes, including 20 from members representing Kosovo's ethnic minorities, prompting 37 deputies of Thaci's Democratic Party of Kosovo (PDK) to leave the session in protest.

Adem Grabovci, head of the PDK's parliamentary group, said Mustafa's election amounted to a coup and promised court action to challenge his appointment.

Thursday's parliament session was the first since snap elections in June that saw the PDK win the largest share of the vote and 37 seats, with Mustafa's Democratic League of Kosovo trailing with 30 MPs.

Despite failing to win an outright majority, Thaci claimed he was entitled to form a new government and for his party to get the speaker's post.

But three opposition parties have joined forces in a bid to form a new government and prevent Thaci from winning a third mandate.

Observers expect the parliamentary deadlock to force President Atifete Jahjaga to delay naming a new prime minister, prolonging a power vacuum that may eventually lead to new early elections.

"We now have a political crisis since the opposition enjoys a majority in parliament and the PDK, which does not want to leave the power, cannot control," political analyst Behlul Beqaj told AFP.

Thaci, an ex-guerilla chief, has dominated politics in Kosovo since it declared independence from Serbia in 2008.