"For two years, I’ve warned about Trump’s reckless lurch towards war with Iran,"
Emily Thornberry wrote in her Twitter account.
"Last night’s attack takes us even closer to the brink," she added.
She noted: "Those of us who marched against the Iraq War must be ready to march again, and ensure we are not dragged into this morass."
The Commander of the IRGC Quds Force and Deputy Commander of the Iraqi Popular Mobilization Units (PMU), known as the Hash al-Shaabi, Abu Mahdi Al-Mohandes were separately leaving Baghdad airport in two cars early Friday morning when they were targeted and assassinated.
Earlier, Iran's Supreme Leader Ayatollah Seyyed Ali Khamenei commented on the martyrdom of the great commander of the IRGC's Quds Force Major General Qasem Soleimani and said harsh and severe revenge is awaiting the criminals.
Martyrdom was his reward for years of implacable efforts. With his departure and with God's power, his work and path will not cease and severe revenge awaits those criminals who have tainted their filthy hands with his blood and the blood of the other martyrs of last night's incident, he said.
The absence of our dear and self-sacrificing Sardar is bitter, but the continuation of the resistance and its final victory will be more bitter for the murderers and criminals.