MPs will be updated on security in Afghanistan following the deaths of three British soldiers and an assault on the UK's main military base in the country over the course of the last few days.

Defence Secretary Philip Hammond is expected to respond to an urgent question from Labour MP Denis MacShane in the House of Commons.

Married father-of-two Sergeant Gareth Thursby, 29, and Private Thomas Wroe, 18, were shot dead in the south of Nahr-e Saraj district, Helmand province, on Saturday, in what appears to be the latest in a string of "green-on-blue" incidents.

The soldiers, from 3rd Battalion, The Yorkshire Regiment (Duke of Wellington's), were killed at a checkpoint when a man dressed as a local Afghan policeman pretended to be injured so they would help him.

On Friday, Lance Corporal Duane Groom, from 1st Battalion Grenadier Guards, died after his vehicle hit a roadside bomb. On the same day, two US Marines were killed during an attack on Camp Bastion, the desert base in Helmand province where the bulk of the UK's 9,500-strong force in Afghanistan are deployed.

Taliban sources later claimed that Bastion was targeted because Prince Harry is serving there on his second tour of duty in the country as an Army captain. The Prince was about two kilometres away with other crew members of an Apache attack helicopter and was not harmed. The attack was by heavily armed insurgents and involved a range of weaponry, including mortars, rockets or rocket-propelled grenades, as well as small arms fire, said US military sources.

This weekend's deaths brought the total number of members of UK forces to have died since operations in Afghanistan began in October 2001 to 430.

Mr Hammond said he was "saddened" to hear of the "cowardly" attack by a man wearing police uniform. The Ministry of Defence said an investigation was under way into the circumstances of the soldiers' deaths.

Sgt Thursby, from Skipton, North Yorkshire, had completed tours of duty in Kosovo and Iraq, and was nicknamed Bull because of his strength and confidence. His wife Louise said: "Gareth was the love of my life. He was an amazing husband and father, happy, full of life and kind-hearted, with a passion for his work and family. He was brave, hard-working, a loving husband who was a devoted father to his children. Our hero."

Pte Wroe was deployed to Afghanistan on July 1, shortly after his 18th birthday. He is survived by his parents, Michael and Claire, and sister Demi, from Holmfirth, West Yorkshire. His family said in a statement: "Our son Thomas was a brave young soldier, who is loved by his family, girlfriend and friends. We can't believe you have been taken so soon from us. You will always be in our hearts for ever and ever. You would light up the room with your smile and bubbly personality. Our world will be a duller place without you. We are so proud of you son, of all you achieved, and we are grateful for every special thing you gave us. We will always love you Tom."