Almost all of the 21 Sudanese opposition parties that were participating in a year-long national dialogue will pull out of the talks, as well as upcoming elections, in the latest sign of deteriorating reconciliation efforts, party representatives have said.

Eighteen opposition parties will not attend a national dialogue meeting with the president on Wednesday, citing worsening political and press freedoms, a statement from the parties said on Tuesday.

President Omar al-Bashir had called for a national dialogue and brought together all political actors last January. However, little progress has been made, and separate negotiations with rebels have faltered.

"We have decided to suspend participation in the national dialogue due to the president's decisions to not release political detainees, allow room for political action, or stop the confiscation of newspapers," said Hassan Osman Rizk, a former minister under Bashir and the current vice president of the Reform Now party.

One opposition party after another has opted to boycott a political process that they say is dominated by Bashir and his circle, who have been in power for 25 years.

The government was not immediately available for comment.

The most prominent of the three parties still participating in the dialogue include the Popular Congress Party (PCP), headed by former Bashir ally Hassan al-Turabi.

'Rushed pull-out'

"The parties that decided to pull out rushed into this decision," said PCP political secretary Kamal Omar. "We will continue for lack of an alternative."

The PCP is still boycotting the April presidential and parliamentary polls, along with all other major opposition parties. The regime has said that elections will continue as planned.

The unraveling political rapprochement in Khartoum takes place against a backdrop of increasing violence in the country's periphery.

The UN has warned of a deteriorating situation in Darfur, as the government has pushed for UN-African Union peacekeepers to exit the war-torn western region.

Negotiators failed last month to reach a ceasefire in a related but separate insurgency in the southern provinces of Blue Nile and South Kordofan mounted mostly by former civil war fighters who were left in Sudan after South Sudan seceded in 2011.

The government has rebuffed opposition and rebel demands to link political negotiations with peace talks.

Local council of Mariupol told Al Jazeera that at least 27 people were killed and dozens more were injured in Saturday's attack.

In a statement, US Secretary of State John Kerry condemned the "horrific assault by Russia-backed separatists".

Kerry blamed the attack on "Russia's irresponsible and dangerous decision to resupply them in recent weeks with hundreds of new pieces of advanced weaponry ... in addition to continuing operational command and control".

Mariupol lies on the Azov Sea and is the major city between mainland Russia and the Russia-annexed Crimean Peninsula.

The pro-Kiev volunteer Azov regiment based around the city said there were "many wounded" in the attack. The Mariupol administration said the rockets hit a large market in one of the city's main residential districts.

"Right now, there are problems with the cell phone network so it is impossible to call relatives who live in that part of town," Mariupol resident Eduard told the AFP news agency.

"Obviously, everyone in the city is very scared. The rebels have already seized the airport. And now they are starting to destroy Mariupol itself."

The attack has raised fears that Russian-backed separatist forces will try to establish a land link between Russia and Crimea.

Rebel forces have positions about 10 km from Mariupol's eastern outskirts.

A massive rebel assault on the port in August led to intense fighting that saw Kiev repel the attack at a heavy cost that soon prompted Ukrainian President Petro Poroshenko to agree to a September 5 truce.

That deal was followed by more clashes that killed at least 1,500 people and was ultimately rejected by the rebels on Friday.

The separatist leader of Donetsk vowed on Friday to escalate the nine-month campaign and seize lands in southeastern Ukraine that are currently under control of the pro-Western authorities.

PHOTO CAPTION

The crisis in Ukraine escalated with a rocket attack that killed dozens. It happened in the port city of Mariupol, which is now a crucial target for the Russian backed rebels who rejected a peace deal with Ukraine. Charlie D'Agata reports.

Aljazeera