By Tarek Amara and Erika Solomon
TUNIS (Reuters) - The head of Tunisia's ruling Islamist party on Thursday refused to remove the prime minister from his post, hardening its stance toward the secular opposition's demand that the government be dissolved.
Earlier this week, leaders from the Ennahda party, which is facing mounting pressure even from its coalition partners, said they were willing to consider creating a new unity government to help ease the political crisis.
Tensions have been rising in Tunisia since the assassination last week of a leftist politician, the second to be slain in six months. The unrest risks disrupting a political transition that began after Tunisians toppled an autocratic president in 2011 and sparked an "Arab Spring" of revolts across the region.
The education minister resigned yesterday and several others threatened to do the same. Ennahda's junior coalition partner, the secular Ettakatol party, is threatening to withdraw if a unity government is not formed.
Ennahda supporters had shown some flexibility on the leadership controversy, but stood firm against the opposition's second demand to dissolve the transitional Constituent Assembly, now weeks away from finishing a draft of a new constitution.
"We are open to new deals ... But the Constituent Assembly is a red line, and we call on all members to return back to their work and complete the constitution," Ennahda party chief Rachid Ghannouchi told the local Mosaique radio station.
"We are holding firm to Ali Larayedh as head of the government."
A series of talks on Thursday between the government and the country's powerful union federation, as well as with the opposition Republican Party, appeared to signal an attempt at detente. Instead, both sides are escalating the face-off, calling for rival mass protests this weekend.
Once upheld as a model of transition among troubled Arab uprisings, Tunisia now risks being plunged into political turmoil and broader instability.
Two days ago, militants ambushed and killed eight soldiers near the Algerian border and two improvised bombs have been set off in Tunis, the first time the capital has seen such attacks, although no one was hurt.
In Tunis, more than 70 lawmakers from the Assembly stopped working and started a sit-in outside the building that has drawn large nightly demonstrations joined by thousands of protesters.
A rival pro-government protest across the square has also drawn sizeable crowds, but on a smaller scale.
Many Tunisians have joined the opposition rallies out of frustration at continued economic stagnation and the country's growing security problems.
Others are angry that the constitution, which the government promised within a year of the Assembly's creation, is now eight months late.
The government was in talks on Thursday with the powerful Tunisian General Labour Union (UGTT), which is mediating for a compromise to bring a new government of technocrats to power.
The UGTT has opposed dissolving the Assembly outright, instead proposing a mechanism to speed up the body's timetable for finishing the constitution and a new election law.
The minister of public affairs, Khalil Zaouia, said the talks were "positive" but gave few other details.
(Editing by Mike Collett-White)