Emergency medical aid is pouring into pandemic-stricken India from around the world as the government seeks to fend off criticism about the slow pace of dispatching supplies to hospitals and states in desperate need.

Dedicated relief flights from countries including the UK, the US, EU member states, Taiwan and Uzbekistan have delivered hundreds of tonnes of supplies, with more expected in the coming days from Israel and elsewhere.

The inflow of oxygen generators, concentrators and cylinders, as well as life-saving drugs and other medical equipment marks the first time India has accepted large-scale international humanitarian aid since the 2004 Boxing Day tsunami, reflecting the magnitude of the crisis.

But Prime Minister Narendra Modi’s government was fiercely criticised by opposition politicians over the slow pace of the aid’s distribution, and the lack of clarity on where the relief is going.

Many hard-hit states reported that they had not received any assistance, and some said much-needed supplies were still sitting in warehouses.

“We request and demand from the government . . . Share it with every Indian: Where has this aid come from, and where is it going?” said Pawan Khera, a spokesperson for the opposition Indian National Congress. “You owe it to the public.”

In a statement on Tuesday, the central government said the authorities were working “24 x 7 to fast track and clear the goods on arrival”.

It listed 38 institutions across India that it said had received equipment. “All possible efforts are done to unpack, repack and dispatch these [goods] with the least possible turn-around time,” it added.

Rudra Chaudhuri, director of the Carnegie India think-tank, said the relief effort had been hampered by the high number of Covid-19 cases among Indian officials.

But he said the government should provide further clarity on which emergency supplies went where, something it did not specify. “It’s a very important issue for donors, recipients and public confidence.”

The official number of coronavirus cases in India soared past 20m on Monday, as more than 350,000 new infections were detected. Although daily cases have declined from a peak of more than 400,000 on Friday, testing has fallen significantly. India’s medical system, including its oxygen supply lines, remains under severe pressure from the sheer number of Covid-19 patients. Even officials involved in the distribution efforts have been hit by the virus.

India had in the recent past refused to accept international relief, which it felt was not in keeping with its own self-image as an emerging global power.

Modi has lately called for non-governmental groups to step up and help respond to the crisis, but global humanitarian organisations say new restrictions imposed on NGO activities last year have hindered their ability to operate.

An overhaul of laws governing foreign charities make it tougher for the likes of Oxfam and Médecins Sans Frontières, and their grassroots partners in rural areas, to receive and use foreign donations.

“In the last year, there have been so many regulations brought in on NGOs, it has really handicapped humanitarian relief work,” said Amitabh Behar, chief executive of Oxfam India, the local arm of the global relief organisation.