Yerevan had accused Azerbaijan of occupying a pocket of its land seized in September in fierce clashes between the neighbours, which left more than 280 people dead.

Armenia is a member of the Collective Security Treaty Organisation (CSTO), a Moscow-led grouping of several ex-Soviet republics.

"We have failed so far to make a decision on CSTO's reaction to Azerbaijan's aggression against Armenia," Pashinyan said Wednesday during the organisation's heads of state summit in Yerevan, which was attended by Russian President Vladimir Putin.

He said it was "depressing that Armenia's membership in the CSTO had failed to contain Azerbaijani aggression."

"This fact is hugely damaging to the CSTO's image both in our country and abroad."

Armenia in September had asked for military help from Moscow, which is obligated under the treaty to defend Armenia in the event of a foreign invasion.

But the Kremlin -- which also has close ties with Baku -- did not rush to help Yerevan.

Pashinyan and Putin are due to meet for talks later Wednesday.

Armenia and Azerbaijan fought two wars -- in the 1990s and in 2020 -- over Azerbaijan's Armenian-populated enclave of Nagorno-Karabakh.

The six weeks of fighting in autumn 2020 claimed the lives of more than 6,500 troops from both sides and ended with a Russian-brokered ceasefire.

Under the deal, Armenia ceded swathes of territory it had controlled for decades, and Moscow deployed about 2,000 Russian peacekeepers to oversee the fragile truce.

Ethnic Armenian separatists in Nagorno-Karabakh broke away from Azerbaijan when the Soviet Union collapsed in 1991. The ensuing conflict claimed around 30,000 lives.