Around 100,000 angry Polish trade unionists marched through Warsaw Saturday in the finale of a four-day protest against the unpopular and increasingly fragile center-right government.

The protest reflects widespread public gloom over a sharp economic slowdown in Poland, which has sent the coalition's popularity plunging to its lowest level since Prime Minister Donald Tusk took office in 2007.

Poland's Muslim community on Tuesday said a controversial nationwide ban on halal and kosher slaughter, which has spurred intense debate at home and abroad, was invalid under European law.

The EU directive "applies in Poland and in this case it supersedes national law," Poland's top Muslim leader, Mufti Tomasz Miskiewicz, said, quoting an expert legal analysis commissioned by the Muslim community and the meat industry.

Sweden and Poland warned against knee-jerk reactions to the crisis in Syria on Saturday, saying that any international effort to solve it will require a commitment "for decades to come".

Speaking at a regional NATO conference in the Latvian capital, Riga, Swedish Foreign Minister Carl Bildt said the West was being short-sighted regarding the instability sweeping the Middle East.

Poland's foreign minister on Friday said Russia was responsible for Syria's Soviet-era chemical weapons and could use its clout to impact the course of the country's conflict.

"Russia keeps stressing that it is against the use of chemical weapons, but we know the Syrian arsenal dates back to the days of the USSR. It's Soviet technology," Foreign Minister Radoslaw Sikorski told reporters in Warsaw.

Poland on Wednesday voiced reservations about military action in Syria, in a rare departure from toeing the same line as the United States.

"I'm not convinced that an armed attack will stop the crimes," Prime Minister Donald Tusk told reporters.

A Polish mother and her boyfriend who systematically starved her four-year-old son before savagely beating him to death were jailed for a minimum of 30 years by a judge on Friday in a case that has horrified Britain.

Magdelena Luczak and Mariusz Krezolek subjected Daniel Pelka to a six-month ordeal in which he was held underwater, locked in a room and force-fed salt before suffering fatal head injuries in a vicious assault.

The detonator and remote control used in a Bulgarian bomb attack that killed five Israelis last year were smuggled in from Poland, a newspaper reported Monday.

The still unidentified bomber and two accomplices smuggled in the components on a train from Warsaw on June 28, the Trud daily said, citing investigators.

Pope Francis announced here Sunday that the next World Youth Day (WYD), the Catholic youth fest, will be held in the Polish city of Krakow in 2016.

"Dear young friends, we have an appointment for the next World Youth Day in 2016 in Krakow, Poland," he said at the end of a mass attended by three million pilgrims on Rio's Copacabana beach.

Polish President Bronislaw Komorowski on Sunday was struck by an egg hurled by a young man during a hugely sensitive visit to Ukraine to commemorate a wartime massacre, police said.

The man went up to Komorowski as he was talking to people at a ceremony in the northwestern city of Lutsk to mark the 70th anniversary of the killings of tens of thousands of Poles by Ukrainian nationalists during World War II.

Hundreds of people were evacuated on Tuesday from hospitals and prosecutor's offices across Poland, including in Warsaw and Krakow, over a series of bomb threats that turned out to be pranks, the interior minister said.

"Twenty-one buildings in Poland received bomb threats," Bartlomiej Sienkiewicz told reporters.