Amnesty International said it was “horrified” at Polish authorities’ “excessive” force against protesters this week – including the use of tear gas.

The human rights group also expressed deep concerns at the detentions of protesters, who have been taking to the streets for weeks to show their anger at a near-total ban on abortion.

The abortion ruling last month was issued by the constitutional court, which is under the political control of the populist conservative ruling party Law and Justice.

Amnesty’s statement came after Polish police used tear gas and force against mostly young, female protesters on Wednesday night. It was a sign of escalating tensions in the country after police started arresting protesters.

It said: “(We are) horrified to see excessive use of force by police, disproportionate charges used against protestors, and speeches from public officials that could encourage further violence toward them.”

Witnesses said that plainclothes officers entered the crowd of protesters on Wednesday night – not all of whom wore armbands identifying them as police – and used telescopic pipes to beat people.

Police said they were using force in response to aggressive protesters. However, Cezary Tomczyk, of the opposing Civil Coalition party, accused police of lying, telling parliament on Thursday that the protesters were peaceful.

Nils Muiznieks, Amnesty’s Europe director, said: “Facing a near-total ban on abortion, people in Poland have mobilised impressively.”

“However, not content with violating their reproductive rights, authorities have used this opportunity to also crack down on their right to peacefully protest.”

Political tensions have been extremely high in Poland since the constitutional court ruled last month to impose a near-total ban on abortion.

The government has yet to publish the ruling in an official journal, which is a formal step required for it to take legal force, amid the huge pressure from the mass street protests.