Four migrants believed to be Iraqi citizens have been found dead near the Poland-Belarus border, authorities in both countries said.
The remains of three men were discovered near Poland’s 248-mile boundary with Belarus, Polish Border Guards said.
Meanwhile, Belarusian authorities found the body of an Iraqi woman only a metre from the border at the weekend.
Poland’s Prime Minister Mateusz Morawiecki said on Facebook that links between these "dramatic events and Belarusian provocations" would be investigated.
He said he was in contact with the interior minister as well as the head of the Border Guards.
A Belarusian border official told state news agency Belta: "On September 19, the body of a woman of non-Slavic appearance was discovered within a metre of the Belarus-Poland border.”
The acting head of the Usovo border post, Yevgeny Omes, said there were "clear signs" on the ground of the body being "dragged" from Poland into Belarus.
Belta reported three children, a man and an elderly woman were found near the body. All five were Iraqi citizens.
The news outlet said the dead woman’s husband claimed that Polish law enforcement drove them to the border and forced them into neighbouring Belarus “under threat”.
One body was discovered by Polish civilians who were picking mushrooms in a forest near the country’s north-eastern border with Belarus and Lithuania. Edyta Pacuk, a spokeswoman for the local police, told regional Radio 5 that a group of people had stumbled upon three Iraqi men in a wooded area, one of whom was dead.
The two other men were taken into police custody and to hospital.
A spokeswoman for Poland’s Border Guards, Anna Michalska, said the remains of two other foreigners were also found near the border with Belarus.
The force said prosecutors have opened investigations to determine how the three people died.
The grim discoveries come as illegal migration continues to blight the border between Belarus and Poland.
On Sunday, three women were among eight migrants who had to be rescued after they got stuck in swamps trying to cross from Belarus into Poland, an EU member state.
Ms Michalska told Polish media border guards were assisted by police, firefighters, military and airborne ambulance service.
Seven of the migrants were taken to hospital.
Lithuania, also a member of the EU, joins Poland in the battle against illegal migration at its border with Belarus.
The two countries agree the influx of migrants amounts to a “hybrid attack” by Belarusian President Alexander Lukashenko’s regime in Minsk that is aimed at destabilising the 27-nation EU.
In August, Polish Prime Minister Mateusz Morawiecki and Lithuanian Prime Minister Ingrida Simonyte released a statement, which read: “We condemn the weaponisation of irregular migration by the Lukashenko regime with a goal of exerting political pressure on the EU and its individual member states.”
Poland and Lithuania, part of the bloc’s eastern frontier, are building razor wire fences, have increased border patrols and introduced a temporary state of emergency along their borders to stop illegal migration.
Ms Michalska said more than 3,800 attempts at illegal crossings from Belarus have been foiled so far in September, more than 320 on Saturday alone.