Pakistan and India are highly alert during airport closures and security drills in major cities

On Pakistan warned that it intends to retaliate against Wednesday’s strike, tensions across India and Pakistan were high, with airport closures and security drills conducted in major border cities.

In a speech on Wednesday night, Prime Minister Shehbaz Sharif said that after India's missile air strike in Pakistan in the early hours of Wednesday morning, he would “sorrowfully swear that we will avenge every drop of blood of our martyrs, killing 31 people.

India's most extensive military attack on Pakistan for decades was nine locations, including four in the Punjab region of Pakistan.

Related: Pakistani Prime Minister promises to “take revenge every drop of blood” after Indian air strikes kill 31

On Thursday morning, Pakistani officials claimed that their air defense system had been shot down for a night as it flew near the airport in the border city of Lahore. India did not comment immediately.

In both countries, flights were suspended and airports were closed. In Pakistan, all flights from Karachi, Lahore and Sialkot airports are suspended until Thursday afternoon. More than 20 local airports in northern India are closed until Saturday.

According to a notice issued by the provincial health department, the Sindh area of ​​Pakistan, which has announced the border with India, has all medical staff and support staff leave cancelled.

In the city of Amritsar, India, 20 miles from the Pakistan border, a second security drill and a brief power outage were conducted on Wednesday night and residents were urged to remain vigilant.

India's border countries in Rajasthan and Punjab were also under high alert, with all police cancelled, and border security forces gave shooting orders for any suspicious activities. India has activated anti-UAV systems near the border.

Sharif called India's attacks an “act of war” and military officials and government ministers vowed to respond to Pakistan. However, by Thursday morning, the nature of the reaction was unclear.

Some government ministers suggested that Pakistan claimed to have shot down five Indian military aircraft, including three French-made Rafale aircraft, in the confrontation on Wednesday, and others said the full response from Pakistan has not yet arrived.

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It is widely acknowledged that the country's Army Director Asim Munir will make any decision on Pakistan's response to India's military, who is under public pressure to make its strength against India.

Ministers of the Indian government said their attacks were retribution for Pakistan's alleged involvement in the radical attack in Kashmir in April, killing 26 people. Pakistan denied any role in the attack.

India claimed Wednesday's strike targeted “terrorist infrastructure”, including training camps and houses belonging to prominent armed groups, which have been some of India's worst terrorist attacks in the past two decades. They stressed that they did not hit any Pakistani military bases or equipment and described the strike as “measurement, escalation, proportionate and responsible”.

However, Pakistan denies that any terrorist group operates in areas attacked by Indian missiles and says the strike is targeted only by civilians.

Along the disputed border between India and Pakistan, separating the disputed areas of Kashmir, with dense cross-border shelling between the two sides continuing until the second night. At least one Indian soldier was reportedly killed in the fire, and 11 civilians and local residents continued to evacuate from the area.

The international community continues to call on both sides to demote. Iranian Foreign Minister Abbas Araghchi landed in Delhi on Thursday morning and he will hold talks with his Indian counterparts. Araghchi visited Pakistan earlier this week and proposed a mediation role between the two countries.