Updated

Tunisian President Moncef Marzouki's secular party is quitting the coalition government in anger at the dominant Islamist party's handling of the country's political crisis.

The move by the Congress for the Republic party threatens to deepen the crisis, prompted by the killing of an opposition leader last week.

Marzouki was a longtime human rights activist whose ascension to the presidency was seen as a sign of Tunisia's democratic progress after it overthrew a longtime authoritarian president in 2011.

The state news agency TAP says the Congress for the Republic party said Sunday that it is quitting the coalition government, which is led by Islamist party Ennahda.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

Calm is returning to the streets of Tunisia's capital, even as pressure is growing on the governing Islamists to find a solution to the country's biggest crisis since it set off the Arab Spring uprisings two years ago.

The killing of a Tunisian opposition leader last week brought protests against a government accused of pandering to extremists. The prime minister wants to appoint a new government of technocrats to ease tensions.

But his Ennahda party rejects the idea. Ennahda's governing committee is meeting Sunday to discuss it, amid signs of a growing split between party moderates and hard-liners.

After three days of street violence, the streets in the capital Tunis are relatively quiet Sunday, under the watchful eye of riot police.