Voters in Tajikistan, the poorest state in the former USSR, were set Wednesday to hand President Emomali Rakhmon an easy victory for a fourth term at the helm of his country bordering Afghanistan.

In a tale all too familiar for elections throughout the Muslim but vehemently secular ex-Soviet states of Central Asia, the five candidates standing against Rakhmon are virtual unknowns even inside the country, with next to no chance of victory.

Police in Tajikistan arrested 10 people suspected of planning a series of attacks to destabilize the country ahead of the presidential polls this year, an official said Saturday.

The suspects, mostly young men who "received training in Pakistan", were seized and disarmed in the capital of Dushanbe, a representative of the Tajikistan interior ministry told Agence France Presse.

China's Xi Jinping at a regional summit signed a deal to build a gas pipeline through the impoverished ex-Soviet country of Tajikistan, Tajik television reported Saturday.

The pipeline will transport gas from energy-rich Turkmenistan to China in as part of a huge supply deal.

Tajikistan on Friday called presidential elections for November, with President Emomali Rakhmon expected to run for another term in the impoverished ex-Soviet country that he has headed for more than two decades.

The country's lower and upper houses of parliament jointly decided to hold elections on November 6, two months before Rakhmon ends his current term.

Tajikistan has ordered local Internet providers to block Twitter, one of more than 100 sites including popular Russian-language social networks starting next week, an industry representative told Agence France Presse Saturday.

"The (government) communications service has sent Internet companies a huge list of 131 sites that must be blocked in the country from Monday," said Asomiddin Atoyev, the head of the Tajik association of Internet providers.

The United Nations warned Friday that nearly 55 million tonnes of radioactive waste from old Soviet-era uranian mines remain in unsecured sites in northern Tajikistan.

The former Soviet republic, where Stalin's empire once mined uranium to create its first nuclear bomb, is still stuck with about 54.8 million tonnes of unsecured waste from the now mainly abandoned mines, the United Nations Economic Commission for Europe (UNECE) said.

Russia on Friday won an effectively free 30-year extension to military base it leases in Tajikistan to police that country's drug and crime-infested border with Afghanistan.

The agreement valid through 2042 was signed by Russian President Vladimir Putin during his visit to the Tajik capital Dushanbe for the 60th birthday celebrations of Tajik leader Emomali Rakhmon.

A suicide bomber tore through a crowd of Afghan demonstrators under a heavy police presence on Monday, killing 16 people in the northern city of Kunduz, officials said.

The attack took place in the main square of the city, the force of the explosives sending police riot gear, pieces of flesh, sandals and turbans flinging across the street.

An ex-warlord in Tajikistan blamed for the murder of a regional security chief has laid down his arms, the interior ministry said Monday, as a truce between rebels and the government appeared to hold.

"The chief of an illegal armed group, Tolib Ayombekov, came in (to give up weapons) after long negotiations with the government," said a ministry spokesman.

Tajik government forces Wednesday declared a temporary ceasefire to allow for talks in a massive military operation in the southeast against militants loyal to an ex-warlord, a military source said.

The ceasefire started at 05:00 GMT and would end at 0900 GMT, the military official told Agence France Presse on condition of anonymity, adding the talks involved Tajik Defense Minister Sherali Khayrulloyev and representatives of the town of Khorog that was the focus of this week's deadly clashes.