Main news of October 31

A roundup of what has happened in the past 24 hours

WORLD

* At least 22 people were injured after a suspected suicide bomber detonated an explosive in Istanbul's main square, local TV reported, referring to police

*The construction of Vietnam's first nuclear power plant will strengthen the country's positions as a strong, independent and modern state, Russian President Dmitry Medvedev said following the signing of a nuclear power deal between the two countries

* Police in Yemeni capital San'a have arrested a woman suspected of sending explosive packages found on U.S.-bound planes

* A Ukrainian opposition party claimed mass violations at local and regional elections, which the ex-Soviet republic was holding

* Ukrainian opposition party Batkyvshchina (Fatherland) plans to challenge in court the results of the local elections in several regions, Mykola Tomenko, deputy head of the party said

* Several people have been detained in Gothenburg and its suburbs on suspicion of being related to the bomb threat in Sweden's second largest city

* Turkey does not believe that its neighbors including Iran poses a threat, Turkey's Foreign Minister Ahmet Davutoglu said

* Vietnam is considering creating a free trade zone with the post-Soviet customs union of Russia, Belarus and Kazakhstan, Vietnam's President Nguyen Minh Triet said

* Brazilians are voting in a presidential runoff to choose the country's new president who will succeed Brazil's popular Luiz Inacio Lula da Silva

RUSSIA

* Russia's Defense Minister Anatoly Serdyukov confirmed the ministry's plans to buy two foreign helicopter carriers for the Russian Navy and eventually produce vessels of this class on Russian soil

* Russia's Armed Forces will undergo three stages of transformation before their reform is over by 2020, Defense Minister Anatoly Serdyukov said

*Sanctioned opposition rally on downtown Moscow's Triumfalnaya Square ran calmly and without major violations, however several protesters tried to hold an own unsanctioned meeting, RIA Novosti correspondent reported

* Moscow's new Mayor Sergey Sobyanin pledged to estimate the work of the city's officials basing upon regular through inspections

* Over 200 young residents of the southwestern Siberian city of Novosibirsk held a Halloween Parade

* Russia switched to winter time at 3:00 a.m. local time, and clocks were set back one hour